Disc apparatus

ABSTRACT

A disc apparatus comprising: a jitter-value detection unit configured to detect a jitter value based on a signal to be read from a medium; a defocus-value setting unit configured to set a defocus value for focusing an objective lens in the medium based on the jitter value; and a defocus-value adjusting unit configured to detect the jitter value every time the defocus value is changed stepwise within a predetermined range of the defocus value including a reference value of the defocus value, to obtain an optimum defocus value to be set for the defocus-value setting unit within a predetermined time period, based on a maximum jitter value and a minimum jitter value of the detected jitter values.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication Nos. 2007-007021, 2007-250379, and 2007-292035, filed Jan.16, 2007, Sep. 27, 2007, and Nov. 9, 2007, respectively, of which fullcontents are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a disc apparatus capable of recording asignal in a medium such as an optical disc with a laser beam appliedfrom an optical pickup device or capable of reproducing a signalrecorded in a medium such as an optical disc with a laser beam.

2. Description of the Related Art

A laser beam applied from an optical pickup device (OPU) of an opticaldisc apparatus is focused on a signal surface of an optical disc. Laser(LASER) is an abbreviation for “light amplification by stimulatedemission of radiation”. A technology of focusing the laser beam on thesignal surface of the optical disc, so-called focusing controltechnology includes various types. In general, the focusing control isperformed by utilizing a signal obtained through a photodetectorincluded in the optical pickup device.

A focus means a focal point or focal spot, for example. Focusing meansbringing into focus or coming into focus. Defocus adjustment in thisdescription means an adjustment operation of focusing for an object outof focus, for example.

According to specifications in which the focusing control is described,for example, there are described a focusing controlling apparatus and afocus pull-in method, where a focus pull-in operation is certainlyperformed in a short period of time for an optical disc with reflectancevarying depending on sates or a phase change optical disc withreflectance varying due to heat of applied light (see, e.g., JapanesePatent Application Laid-Open Publication No. 2002-342948 (pages 1, 3 to5, FIGS. 1 to 5)).

The focusing control is generally performed by a circuit called afocusing servo circuit and the displacement operation of an objectivelens is performed based on a position that is the center of theoperation of the objective lens, for example. A servo means, forexample, those including a mechanism performing automatic correctioncontrol with measuring a state of a control target to be compared with apredetermined reference value.

For example, some optical pickup devices include a system where anarbitrary offset (OFFSET) can be applied by a focus mechanism, andjitter (jitter) is adjusted at the time of reading data from a disc(DISC) based on focus offset (FOCUS_OFFSET) that is the so-calleddefocus (DEFOCUS). The jitter means slight fluctuation and distortion ofa signal, for example.

For example, in some optical pickup devices, a jitter value included ina signal such as a reproduction signal is detected to adjust theoperational center position of the objective lens (see, e.g., JapanesePatent Application Laid-Open Publication No. Hei7-262584 (pages 1 and 2,FIGS. 1 to 6)).

In optical pickup devices, an F-bias (F BIAS) value, which is a bias(BIAS) value of the focus (FOCUS), so-called defocus value, is renderedvariable so that the defocus value is set at the optimum jitter value.

For example, in some optical disc reading apparatuses, there can beobtained a focus bias amount corresponding to an optical disc bydetecting a correlation between a focus bias value displacing areference position of the focus of a pickup and a jitter value of dataread by the pickup (see, e.g., Japanese Patent Application Laid-OpenPublication No. 10-228652 (pages 1 and 2, FIGS. 1 to 8)).

The focusing control in the optical disc apparatus is performed with theuse of a focusing error signal obtained by the photodetector. If theobjective lens is displaced substantially in a direction orthogonal to asurface of the optical disc by the focusing control, a focusing errorsignal called S-shaped curve can be obtained as described in patentdocument 1, for example. If the level of the focusing error signal fallswithin a focusing controllable range in which a point called zero-crossof the S-shaped curve is the center, the focusing servo operation isperformed to execute the focusing control. By performing the focusingservo operation, a laser beam applied from a laser diode is focused onthe signal surface of the optical disc.

A technology of setting a focal point of a laser beam on a substantiallyspiral track provided on a signal surface of an optical disc, so-calledtracking control technology includes various types. In general, thetracking control is performed by utilizing a signal obtained through thephotodetector included in the optical pickup device.

In this description, a track means a track of signal in an optical disc,for example. Tracking means tracking a micro signal portion provided onthe signal surface of the optical disc with the use of light to set aposition on a substantially spiral-shaped track.

According to specifications in which the tracking control is described,for example, there are described a rotation correction circuit, asemiconductor integrated circuit, an optical disc device, and a rotationcorrection method, which: achieve a good information data readingperformance even at the time of high-speed rotation of an optical discwith eccentricity or wobbling; and are able to stably execute trackjumps and layer jumps (see, e.g., Japanese Patent Application Laid-OpenPublication No. 2003-263760 (pages 1 and 5, FIGS. 1 to 29)).

The tracking control is generally performed by a circuit called atracking servo circuit and the displacement operation of the objectivelens is performed based on a position that is the center of theoperation of the objective lens, for example.

For example, some optical pickup devices include a system where anarbitrary offset (OFFSET) can be applied by a track mechanism, andjitter (jitter) is adjusted at the time of reading data from a disc(DISC) based on track offset (TRACK_OFFSET) that is the so-calleddetrack (DETRACK).

In optical pickup devices, a T-bias (T BIAS) value, which is a bias(BIAS) value of the track (TRACK), so-called detrack value, is normallyrendered variable so that the detrack value is set at the optimum jittervalue.

For example, there has been devised an optical disc apparatus thatinvariably sets a track bias amount with calculation processes. Forexample, there has been also devised an optical disc apparatus that setsa track bias amount based on the minimum jitter value.

In conventional optical disc apparatuses including a tilt mechanism ortilt function, correction of skew in a radial direction of a disc (disc)and correction of recording quality are facilitated. The tilt (tilt) inoptical disc apparatuses or optical pickup devices means angle deviationbetween a disc surface and a light axis of the objective lens. The skew(skew) means “deformation” and “bending”.

For example, some optical pickup devices include a system where anarbitrary offset (OFFSET) can be applied by a tilt mechanism, and toadjust jitter (jitter) is adjusted at the time of reading data from adisc (DISC) based on tilt offset (TILT_OFFSET) that is the so-calledtilt (TILT).

The above apparatuses provided with the tilt function include an opticalhead device not requiring addition of power feeding wires to a lensholder and not causing increase in size and weight of the lens holder(see, e.g., Japanese Patent Application Laid-Open Publication No.2002-197698 (pages 1 and 2, FIGS. 1 to 3)).

In optical pickup devices, a tilt value is normally rendered variable sothat the tilt value is set at the optimum jitter value. For example,there has been devised an optical disc apparatus that invariably sets atilt bias amount with calculation processes. For example, there has beenalso devised an optical disc apparatus that sets a tilt bias amountbased on the minimum jitter value.

In the above optical pickup device, there is a problem that a focusposition obtained by control of the focusing servo operation is notalways the best focal point due to an individual difference of anoptical pickup device itself or an optical disc, so that the focusingservo operation is not performed in the optimum state.

To solve the above problem, for example, there has been proposed anoptical disc reading apparatus described in the patent document 3.However, in an optical disc reading apparatus described in JapanesePatent Application Laid-Open Publication No. 10-228652, for example,since the focus bias amount is set through a calculation process, thetime required for the setting process is prolonged, which may be aproblem.

For example, when performing a method of setting the focus bias amountbased on the minimum jitter value, the following problems may occur. Forexample, among optical discs to be used, there are optical discs forwhich jitter value changes very slightly. A bias amount set in the caseof such an optical disc may be a focus bias amount at the edge ofdetection range. When the focus bias amount is set in this way, thefocusing servo operation becomes unsteady, which is a problem.

Specifically, in some optical discs, a jitter value corresponding to adefocus value may not substantially be changed when the defocus value isadjusted by the optical pickup device, or a jitter value enabling steadyreading operation is obtained even if a defocus value is set to zero. Ifa biased defocus value is set in accordance with the optimum jitter forsuch optical discs, the servo becomes unsteady due to this defocusvalue, resulting in focus drop, so-called F-drop, etc.

The focus drop means, for example, that a focus of a laser beam emittedfrom an optical pickup device deviates from a pit portion of a disc in astate of being tracked, so that data recorded in the disc becomes unableto be read. A pit means a hole or a dent portion.

For example, when the defocus adjustment is performed based on thedetected jitter, the F-drop may occur in an optical pickup device havingslight changes in jitter. When the defocus adjustment is performed in anoptical pickup device having slight changes in jitter, a defocus valuemay be set at a value apart from the center value corresponding to thecenter of the operation of the objective lens. If such a setting isperformed, the F-drop may occur in the optical pickup device.

When the defocus adjustment is performed in an optical pickup device, ifa value other than zero is set as the defocus value, a problem occursthat a track may not be caught when the optical pickup device performs atrack jump on an optical disc.

In the conventional optical pickup device, there is a problem that afocus position obtained by control of the tracking servo operation isnot always the best focal point due to an individual difference of anoptical pickup device itself or an optical disc and, so that thetracking servo operation is not performed in the optimum state.

For example, in the optical disc apparatuses setting the track biasamount through a calculation process, since the track bias amount is setthrough a calculation process, the time required for the setting processis prolonged, which may be a problem.

For example, when performing a method of setting the track bias amountbased on the minimum jitter value, the following problems may occur. Forexample, among optical discs to be used, there are optical discs forwhich jitter value changes very slightly. A bias amount set in the caseof such an optical disc may be a track bias amount at the edge ofdetection range. When the track bias amount is set in this way, thetracking servo operation becomes unsteady, which is a problem.

In some optical discs, a jitter value corresponding to a detrack valuemay not substantially be changed when the detrack value is adjusted bythe optical pickup device, or a jitter value enabling steady readingoperation is obtained even if a detrack value is set to zero. If abiased detrack value is set in accordance with the optimum jitter forsuch optical discs, the servo becomes unsteady due to this detrackvalue, which may result in track skip, etc.

The track skip means, for example, that a focus of a laser beam emittedfrom an optical pickup device deviates from a track portion of a disc ina state of being tracked, so that data recorded in the disc becomesunable to be read.

For example, when the detrack adjustment is performed based on thedetected jitter, the track skip may occur in an optical pickup devicehaving slight changes in jitter. When the detrack adjustment isperformed in an optical pickup device having slight changes in jitter, adetrack value may be set at a value apart from the center valuecorresponding to the center of the operation of the objective lens. Ifsuch a setting is performed, the track skip may occur in the opticalpickup device.

When the detrack adjustment is performed in an optical pickup device, ifa value other than zero is set as the detrack value, a problem occursthat a track may not be caught when the optical pickup device performs atrack jump on an optical disc.

In the conventional optical pickup device, there is a problem that afocus position obtained by control of the focusing servo operation isnot always the best focal point due to an individual difference of anoptical pickup device itself or an optical disc, so and that the tiltoperation is not performed in the optimum state.

For example, in the optical disc apparatuses setting the tilt biasamount through a calculation process, since the tilt bias amount is setthrough a calculation process, the time required for the setting processis prolonged, which may be a problem.

For example, when performing a method of setting the tilt bias amountbased on the minimum jitter value, the following problems may occur. Forexample, among optical discs to be used, there are optical discs forwhich jitter value changes very slightly. A bias amount set in the caseof such an optical disc may be a tilt bias amount at the edge ofdetection range. When the tilt bias amount is set in this way, the tiltoperation becomes unsteady, which is a problem.

In some optical discs, a jitter value corresponding to a tilt value maynot substantially be changed when the tilt value is adjusted by theoptical pickup device, or a jitter value enabling steady readingoperation is obtained even if a tilt value is set to zero. If a biasedtilt value is set in accordance with the optimum jitter for such opticaldiscs, the servo becomes unsteady due to this tilt value, resulting inservo failure, etc.

For example, when the tilt adjustment is performed based on the detectedjitter, the servo failure may occur in an optical pickup device havingslight changes in jitter. When the tilt adjustment is performed in anoptical pickup device having slight changes in jitter, a tilt value maybe set at a value apart from the center value corresponding to thecenter of the operation of the objective lens. If such a setting isperformed, the servo failure may occur in the optical pickup device.

When the tilt adjustment is performed in an optical pickup device, if avalue other than zero is set as the tilt value, the servo failure tendsto occur when the optical pickup device performs a track jump on anoptical disc, which is a problem.

SUMMARY OF THE INVENTION

A disc apparatus according to an aspect of the present invention,comprises: a jitter-value detection unit configured to detect a jittervalue based on a signal to be read from a medium; a defocus-valuesetting unit configured to set a defocus value for focusing an objectivelens in the medium based on the jitter value; and a defocus-valueadjusting unit configured to detect the jitter value every time thedefocus value is changed stepwise within a predetermined range of thedefocus value including a reference value of the defocus value, toobtain an optimum defocus value to be set for the defocus-value settingunit within a predetermined time period, based on a maximum jitter valueand a minimum jitter value of the detected jitter values.

Other features of the present invention will become apparent fromdescriptions of this specification and of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For more thorough understanding of the present invention and advantagesthereof, the following description should be read in conjunction withthe accompanying drawings, in which:

FIG. 1 is a configuration view of a disc apparatus according to anembodiment of the present invention;

FIG. 2 is an explanatory view of an operating state of a wobbling discconsidered as a medium disposed in a disc apparatus;

FIG. 3 is a waveform chart of an oscillation period when rotating awobbling disc considered as a medium;

FIG. 4A is an explanatory view of an operating state of an eccentricdisc considered as a medium disposed in a disc apparatus when anobjective lens is tilted toward disc outer circumference of an eccentricdisc;

FIG. 4B is an explanatory view of an operating state of an eccentricdisc considered as a medium disposed on a disc apparatus when anobjective lens is tilted toward disc inner circumference of an eccentricdisc;

FIG. 5 is a waveform chart of an oscillation period when rotating aneccentric disc considered as a medium;

FIG. 6A is a flowchart of an embodiment of a defocus-value adjustingmethod of a disc apparatus;

FIG. 6B is a flowchart of a jitter-value detecting process of adefocus-value adjusting method of a disc apparatus;

FIG. 7 is a flowchart of a track jump process when performing adefocus-value adjusting method of a disc apparatus;

FIG. 8 is a graphical representation of a relationship between a defocusvalue and a jitter value;

FIG. 9 is also a graphic representation of a relationship between adefocus value and a jitter value;

FIG. 10 is also a graphic representation of a relationship between adefocus value and a jitter value;

FIG. 11 is also a graphic representation of a relationship between adefocus value and a jitter value;

FIG. 12 is also a graphic representation of a relationship between adefocus value and a jitter value;

FIG. 13A is a flowchart of an embodiment of a detrack-value adjustingmethod of a disc apparatus;

FIG. 13B is a flowchart of a jitter-value detecting process of adetrack-value adjusting method of a disc apparatus;

FIG. 14 is a flowchart of a track jump process when performing adetrack-value adjusting method of a disc apparatus;

FIG. 15 is a graphical representation of a relationship between adetrack value and a jitter value;

FIG. 16 is also a graphic representation of a relationship between adetrack value and a jitter value;

FIG. 17 is also a graphic representation of a relationship between adetrack value and a jitter value;

FIG. 18 is also a graphic representation of a relationship between adetrack value and a jitter value;

FIG. 19 is also a graphic representation of a relationship between adetrack value and a jitter value;

FIG. 20A is a flowchart of an embodiment of a tilt-value adjustingmethod of a disc apparatus;

FIG. 20B is a flowchart of a jitter-value detecting process of thetilt-value adjusting method of a disc apparatus;

FIG. 21 is a flowchart of a track jump process when performing atilt-value adjusting method of a disc apparatus;

FIG. 22 is a graphic representation of a relationship between a tiltvalue and a jitter value;

FIG. 23 is also a graphic representation of a relationship between atilt value and a jitter value;

FIG. 24 is also a graphic representation of a relationship between atilt value and a jitter value;

FIG. 25 is also a graphic representation of a relationship between atilt value and a jitter value; and

FIG. 26 is also a graphic representation of a relationship between atilt value and a jitter value.

DETAILED DESCRIPTION OF THE INVENTION

At least the following details will become apparent from descriptions ofthis specification and of the accompanying drawings.

In a disc apparatus detecting a jitter value of a signal read from amedium and adjusting the position of an objective lens for the mediumbased on the jitter value with the use of an optical pickup deviceincluding an objective lens according to one embodiment of the presentinvention, when focusing the objective lens in the medium based on thejitter value, there is adjusted a defocus value used for moving theobjective lens in the light axis direction of the objective lens, toperform the focusing adjustment of the objective lens for the medium,and on this occasion, the jitter value is detected as needed every timethe defocus value is changed stepwise within a predetermined range ofnumeric values including the reference value of the defocus value, toset an optimum defocus value within substantially 20 seconds based on adifference value between the maximum jitter value and the minimum jittervalue of the detected jitter values.

The optimum defocus value is set in a disc apparatus with the aboveconfiguration. Since the jitter value is detected as needed every timethe defocus value is changed stepwise within the predetermined range ofnumeric values including a reference value of the defocus value, to setthe optimum defocus value based on the difference value between themaximum jitter value and the minimum jitter value of the detected jittervalues, the optimum defocus value is set in the disc apparatus. Thedefocus adjustment is performed in the disc apparatus without waitingfor a long time due to the defocus adjustment. Since the defocusadjustment is performed within substantially 20 seconds when performingthe defocus adjustment of the objective lens for the medium, a situationis avoided where one must wait for a long time due to the defocusadjustment performed by the disc apparatus.

In the disc apparatus according to one embodiment of the presentinvention, when performing the defocus adjustment of the objective lensfor the medium, if it is determined that the difference value betweenthe maximum jitter value and the minimum jitter value is a value greaterthan a predetermined value, the defocus value corresponding to theminimum jitter value is set as the optimum defocus value.

With the above configuration, the optical pickup device making up thedisc apparatus performs the stable focusing servo operation for themedium. The medium, when it is determined that the difference valuebetween the maximum jitter value therefor and the minimum jitter valuetherefor is a value greater than the predetermined value, is consideredas the medium with poor jitter characteristics. Since the defocus valuecorresponding to the minimum jitter value is set as the optimum defocusvalue when reading a signal from the medium with poor jittercharacteristics, the stable focusing servo operation is performed in theoptical pickup device.

In the disc apparatus according to one embodiment of the presentinvention, when performing the defocus adjustment of the objective lensfor the medium, if it is determined that the difference value betweenthe maximum jitter value and the minimum jitter value is a small valuethat is equal to or smaller than a predetermined value, the referencevalue of the defocus value is set as the optimum defocus value.

With the above configuration, the optical pickup device making up thedisc apparatus performs the stable focusing servo operation for themedium. The medium, when it is determined that the difference valuebetween the maximum jitter value therefor and the minimum jitter valuetherefor is a small value that is equal to or smaller than thepredetermined value, is considered as the medium with good jittercharacteristics. Since the reference value of the defocus value is setas the optimum defocus value in the disc apparatus when reading a signalfrom the medium with good jitter characteristics, the stable focusingservo operation is performed in the optical pickup device withoutfailure occurring in the focusing servo operation of the optical pickupdevice.

In the disc apparatus according to one embodiment of the presentinvention, when performing the defocus adjustment of the objective lensfor the medium, the jitter value is first detected based on thereference value of the defocus value, and if it is determined that thedetected jitter value is a value greater than a predetermined jittervalue, the jitter value is detected every time the defocus value ischanged stepwise within the predetermined range of numeric valuesincluding the reference value of the defocus value.

The optimum defocus value corresponding to the medium is set in the discapparatus with the above configuration. When performing the defocusadjustment of the objective lens for the medium, the jitter value isfirst detected based on the reference value of the defocus value. Themedium, when it is determined that the jitter value therefor based onthe reference value of the defocus value is a value greater than thepredetermined jitter value, is considered as the medium having a needfor checking each of the jitter values corresponding to each of thedefocus values. If it is determined that the detected jitter value basedon the reference value of the defocus value is a value greater than thepredetermined jitter value, the jitter value is detected every time thedefocus value is changed stepwise within the predetermined range ofnumeric values including the reference value of the defocus value, andthe optimum defocus value corresponding to the medium is set based onthe difference value between the maximum jitter value and the minimumjitter value of the detected jitter values.

In the disc apparatus according to one embodiment of the presentinvention, when performing the defocus adjustment of the objective lensfor the medium, the jitter value is first detected based on thereference value of the defocus value, and if it is determined that thedetected jitter value is a small value equal to or smaller than apredetermined jitter value, the reference value of the defocus value isset as the optimum defocus value without detecting each of the jittervalues every time the defocus value is changed stepwise within apredetermined range of numeric values including the reference value ofthe defocus value.

With the above configuration, the defocus value is swiftly set when themedium with good jitter characteristics is used, and the optical pickupdevice making up the disc apparatus performs the stable focusing servooperation for the medium. When performing the defocus adjustment of theobjective lens for the medium, the jitter value is first detected basedon the reference value of the defocus value. The medium, when it isdetermined that the jitter value therefor based on the reference valueof the defocus value is a small value that is equal to or smaller thanthe predetermined jitter value, is considered as the medium with goodjitter characteristics. Since the reference value of the defocus valueis set as the optimum defocus value without detecting each of the jittervalues every time the defocus value is changed stepwise within thepredetermined range of numeric values including the reference value ofthe defocus value when reading a signal from the medium with good jittercharacteristics, the setting time of the defocus value is reduced. Sincethe reference value of the defocus value is set as the optimum defocusvalue in the disc apparatus when reading a signal from the medium withgood jitter characteristics, the stable focusing servo operation isperformed in the optical pickup device without failure occurring in thefocusing servo operation of the optical pickup device.

In the disc apparatus according to one embodiment of the presentinvention, in the case where the optimum defocus value is set to thenumeric value other than the reference value, when a track jump isperformed by the optical pickup device on the medium, the defocus valueis set to the reference value.

With the above configuration, even if the numeric value other than thereference value is set as the optimum defocus value in the discapparatus, the track jump of the optical pickup device on the medium isfavorably performed. If the defocus adjustment of the optical pickupdevice is performed for the medium and the defocus value is set to thenumeric value other than the reference value, a track may not be caughtwhen the track jump is performed by the optical pickup device on themedium. However, even if the defocus value is set to the numeric valueother than the reference value, since the defocus value is set to thereference value when the track jump is performed by the optical pickupdevice, the track jump becomes easily performed by the optical pickupdevice on the medium in a more normal manner.

In the disc apparatus according to one embodiment of the presentinvention, the defocus value is returned to the numeric value other thanthe reference value after the track jump of the optical pickup device onthe medium is completed.

With the above configuration, the optimum defocus value is again set inthe disc apparatus. When the track jump of the optical pickup device onthe medium is not performed, the numeric value other than the referencevalue of the defocus value is again set as the optimum defocus value inthe disc apparatus and, therefore, the focusing adjustment of theobjective lens for the medium is favorably performed.

In a disc apparatus detecting a jitter value of a signal read from amedium and adjusting the position of an objective lens for the mediumbased on the jitter value with the use of an optical pickup devicehaving the objective lens according to one embodiment of the presentinvention, when focusing the objective lens in the medium based on thejitter value, there is adjusted a detrack value used for moving theobjective lens in the radial direction of the medium, to perform thetracking adjustment of the objective lens for the medium, and on thisoccasion, the jitter value is detected as needed every time the detrackvalue is changed stepwise within a predetermined range of numeric valuesincluding a reference value of the detrack value, to set an optimumdetrack value within substantially 20 seconds based on a differencevalue between the maximum jitter value and the minimum jitter value ofthe detected jitter values.

The optimum detrack value is set in a disc apparatus with the aboveconfiguration. Since the jitter value is detected as needed every timethe detrack value is changed stepwise within the predetermined range ofnumeric values including the reference value of the detrack value, toset the optimum detrack value based on the difference value between themaximum jitter value and the minimum jitter value of the detected jittervalues, the optimum detrack value is set in the disc apparatus. Thedetrack adjustment is performed in the disc apparatus without waitingfor a long time due to the detrack adjustment. Since the detrackadjustment is performed within substantially 20 seconds when performingthe detrack adjustment of the objective lens for the medium, a situationis avoided where one must wait for a long time due to the detrackadjustment performed by the disc apparatus.

In the disc apparatus according to one embodiment of the presentinvention, when performing the detrack adjustment of the objective lensfor the medium, if it is determined that the difference value betweenthe maximum jitter value and the minimum jitter value is a value greaterthan a predetermined value, the detrack value corresponding to theminimum jitter value is set as the optimum detrack value.

With the above configuration, the optical pickup device making up thedisc apparatus performs the stable tracking servo operation for themedium. The medium, when it is determined that the difference valuebetween the maximum jitter value therefor and the minimum jitter valuetherefor is a value greater than the predetermined value, is consideredas the medium with poor jitter characteristics. Since the detrack valuecorresponding to the minimum jitter value is set as the optimum detrackvalue when reading a signal from the medium with poor jittercharacteristics, the stable tracking servo operation is performed in theoptical pickup device.

In the disc apparatus according to one embodiment of the presentinvention, when performing the detrack adjustment of the objective lensfor the medium, if it is determined that the difference value betweenthe maximum jitter value and the minimum jitter value is a small valuethat is equal to or smaller than a predetermined value, the referencevalue of the detrack value is set as the optimum detrack value.

With the above configuration, the optical pickup device making up thedisc apparatus performs the stable tracking servo operation for themedium. The medium, when it is determined that the difference valuebetween the maximum jitter value therefor and the minimum jitter valuetherefor is a small value equal to or smaller than the predeterminedvalue, is considered as the medium with good jitter characteristics.Since the reference value of the detrack value is set as the optimumdetrack value in the disc apparatus when reading a signal from themedium with good jitter characteristics, the stable tracking servooperation is performed in the optical pickup device without failureoccurring in the tracking servo operation of the optical pickup device.

In the disc apparatus according to one embodiment of the presentinvention, when performing the detrack adjustment of the objective lensfor the medium, the jitter value is first detected based on thereference value of the detrack value, and if it is determined that thedetected jitter value is a value greater than a predetermined jittervalue, the jitter value is detected every time the detrack value ischanged stepwise within the predetermined range of numeric valuesincluding the reference value of the detrack value.

The optimum detrack value corresponding to the medium is set in the discapparatus with the above configuration. When performing the detrackadjustment of the objective lens for the medium, the jitter value isfirst detected based on the reference value of the detrack value. Themedium, when it is determined that the jitter value therefor based onthe reference value of the detrack value is a value greater than thepredetermined jitter value, the medium is considered as the mediumhaving a need for checking each of the jitter values corresponding toeach of the detrack values. If it is determined that the detected jittervalue based on the reference value of the detrack value is a valuegreater than the predetermined jitter value, the jitter value isdetected every time the detrack value is changed stepwise within thepredetermined range of numeric values including the reference value ofthe detrack value, and the optimum detrack value corresponding to themedium is set based on the difference value between the maximum jittervalue and the minimum jitter value of the detected jitter values.

In the disc apparatus according to one embodiment of the presentinvention, when performing the detrack adjustment of the objective lensfor the medium, the jitter value is first detected based on thereference value of the detrack value, and if it is determined that thedetected jitter value is a small value equal to or smaller than apredetermined jitter value, the reference value of the detrack value isset as the optimum detrack value without detecting each of the jittervalues every time the detrack value is changed stepwise within thepredetermined range of numeric values including the reference value ofthe detrack value.

With the above configuration, the detrack value is swiftly set when themedium with good jitter characteristics is used, and the optical pickupdevice making up the disc apparatus performs the stable tracking servooperation for the medium. When performing the detrack adjustment of theobjective lens for the medium, the jitter value is first detected basedon the reference value of the detrack value. The medium, when it isdetermined that the jitter value therefor based on the reference valueof the detrack value is a small value equal to or smaller than thepredetermined jitter value, is considered as the medium with good jittercharacteristics. Since the reference value of the detrack value is setas the optimum detrack value without detecting each of the jitter valuesevery time the detrack value is changed stepwise within a predeterminedrange of numeric values including the reference value of the detrackvalue when reading a signal from the medium with good jittercharacteristics, the setting time of the defocus value is reduced. Sincethe reference value of the detrack value is set as the optimum detrackvalue in the disc apparatus when reading a signal from the medium withgood jitter characteristics, the stable tracking servo operation isperformed in the optical pickup device without failure occurring in thetracking servo operation of the optical pickup device.

In the disc apparatus according to one embodiment of the presentinvention, in the case where the optimum detrack value is set to thenumeric value other than the reference value, when a track jump isperformed by the optical pickup device on the medium, the detrack valueis set to the reference value.

With the above configuration, even if the numeric value other than thereference value is set as the optimum detrack value in the discapparatus, the track jump of the optical pickup device is suitablyperformed on the medium. If the detrack adjustment of the optical pickupdevice for the medium is performed and the detrack value is set to thenumeric value other than the reference value, a track may not be caughtwhen the track jump is performed by the optical pickup device on themedium. However, even if the detrack value is set to the numeric valueother than the reference value, since the detrack value is set to thereference value when the track jump is performed by the optical pickupdevice the track jump becomes easily performed by the optical pickupdevice on the medium in a more normal manner.

In the disc apparatus according to one embodiment of the presentinvention, the detrack value is returned to the numeric value other thanthe reference value after the track jump of the optical pickup device onthe medium is completed.

With the above configuration, the optimum detrack value is again set inthe disc apparatus. When the track jump of the optical pickup device onthe medium is not performed, the numeric value other than the referencevalue of the detrack value is again set as the optimum detrack value inthe disc apparatus and, therefore, the tracking adjustment of theobjective lens for the medium is favorably performed.

In a disc apparatus detecting a jitter value of a signal read from amedium and adjusting the position of an objective lens for the mediumbased on the jitter value with the use of an optical pickup devicehaving an objective lens according to one embodiment of the presentinvention, when focusing the objective lens in the medium based on thejitter value, there is adjusted a tilt value used for correcting theangle deviation of the objective lens for the signal layer of themedium, to perform the tilt adjustment of the objective lens for themedium, and on this occasion, the jitter value is detected as neededevery time the tilt value is changed stepwise within a predeterminedrange of numeric values including a reference value of the tilt value,to set the optimum tilt value within substantially 20 seconds based on adifference value between the maximum jitter value and the minimum jittervalue of the detected jitter values.

The optimum tilt value is set in a disc apparatus with the aboveconfiguration. Since the jitter value is detected as needed every timethe tilt value is changed stepwise within the predetermined range ofnumeric values including the reference value of the tilt value, to setthe optimum tilt value based on the difference value between the maximumjitter value and the minimum jitter value of the detected jitter values,the optimum tilt value is set in the disc apparatus. The tilt adjustmentis performed in the disc apparatus without waiting for a long waitingtime due to the tilt adjustment. Since the tilt adjustment is performedwithin substantially 20 seconds when performing the tilt adjustment ofthe objective lens for the medium, a situation is avoided where one mustwait for a long time due to the tilt adjustment performed by the discapparatus.

In the disc apparatus according to one embodiment of the presentinvention, when performing the tilt adjustment of the objective lens forthe medium, if it is determined that the difference value between themaximum jitter value and the minimum jitter value is a value greaterthan a predetermined value, the tilt value corresponding to the minimumjitter value is set as the optimum tilt value.

With the above configuration, the optical pickup device making up thedisc apparatus performs the stable tilt operation for the medium. Themedium, when it is determined that the difference value between themaximum jitter value therefor and the minimum jitter value therefor is avalue greater than the predetermined value, is considered as the mediumwith poor jitter characteristics. Since the tilt value corresponding tothe minimum jitter value is set as the optimum tilt value when reading asignal from the medium with poor jitter characteristics, the stable tiltoperation is performed in the optical pickup device.

In the disc apparatus according to one embodiment of the presentinvention, when performing the tilt adjustment of the objective lens forthe medium, if it is determined that the difference value between themaximum jitter value and the minimum jitter value is a small value equalto or smaller than a predetermined value, the reference value of thetilt value is set as the optimum tilt value.

With the above configuration, the optical pickup device making up thedisc apparatus performs the stable tilt operation for the medium. Themedium, when it is determined that the difference value between themaximum jitter value therefor and the minimum jitter value therefor is asmall value equal to or smaller than the predetermined value, isconsidered as the medium with good jitter characteristics. Since thereference value of the tilt value is set as the optimum tilt value inthe disc apparatus when reading a signal from the medium with goodjitter characteristics, the stable tilt operation is performed in theoptical pickup device without failure occurring in the tilt operation ofthe optical pickup device.

In the disc apparatus according to one embodiment of the presentinvention, when performing the tilt adjustment of the objective lens forthe medium, the jitter value is first detected based on the referencevalue of the tilt value, and if it is determined that the detectedjitter value is a value greater than a predetermined jitter value, thejitter value is detected every time the tilt value is changed stepwisewithin the predetermined range of numeric values including the referencevalue of the tilt value.

The optimum tilt value corresponding to the medium is set in the discapparatus with the above configuration. When performing the tiltadjustment of the objective lens for the medium, the jitter value isfirst detected based on the reference value of the tilt value. Themedium, when it is determined that the jitter value therefor based onthe reference value of the tilt value is a value greater than thepredetermined jitter value, is considered as the medium having a needfor checking each of the jitter values corresponding to each of the tiltvalues. If it is determined that the detected jitter value based on thereference value of the tilt value is a value greater than thepredetermined jitter value, the jitter value is detected every time thetilt value is changed stepwise within the predetermined range of numericvalues including the reference value of the tilt value, and the optimumtilt value corresponding to the medium is set based on the differencevalue between the maximum jitter value and the minimum jitter value ofthe detected jitter values.

In the disc apparatus according to one embodiment of the presentinvention, when performing the tilt adjustment of the objective lens forthe medium, the jitter value is first detected based on the referencevalue of the tilt value, and if it is determined that the detectedjitter value is a small value equal to or smaller than a predeterminedjitter value, the reference value of the tilt value is set as theoptimum tilt value without detecting the jitter value every time thetilt value is changed stepwise within a predetermined range of numericvalues including the reference value of the tilt value.

With the above configuration, the tilt value is swiftly set when themedium with good jitter characteristics is used, and the optical pickupdevice making up the disc apparatus performs the stable tilt operationfor the medium. When performing the tilt adjustment of the objectivelens for the medium, the jitter value is first detected based on thereference value of the tilt value. The medium, when it is determinedthat the jitter value therefor based on the reference value of the tiltvalue is a small value equal to or smaller than the predetermined jittervalue, is considered as the medium with good jitter characteristics.Since the reference value of the tilt value is set as the optimum tiltvalue without detecting each of the jitter values every time the tiltvalue is changed stepwise of numeric values within the predeterminedrange including the reference value of the tilt value when reading asignal from the medium with good jitter characteristics, the settingtime of the tilt value is reduced. Since the reference value of the tiltvalue is set as the optimum tilt value in the disc apparatus whenreading a signal from the medium with good jitter characteristics, thestable tilt operation is performed in the optical pickup device withoutfailure occurring in the tilt operation of the optical pickup device.

In the disc apparatus according to one embodiment of the presentinvention, in the case where the optimum tilt value is set to thenumeric value other than the reference value, when a track jump isperformed by the optical pickup device on the medium, the tilt value isset to the reference value.

With the above configuration, even if the numeric value other than thereference value is set as the optimum tilt value in the disc apparatus,the track jump of the optical pickup device on the medium is favorablyperformed. If the tilt adjustment of the optical pickup device isperformed for the medium and the tilt value is set to the numeric valueother than the reference value, the servo failure tends to occur.However, even if the tilt value is set to the numeric value other thanthe reference value, since the tilt value is set to the reference valuewhen the track jump is performed by the optical pickup device, the trackjump becomes easily performed by the optical pickup device on the mediumin a more normal manner.

In the disc apparatus according to one embodiment of the presentinvention, the tilt value is returned to the numeric value other thanthe reference value after the track jump of the optical pickup device onthe medium is completed in the disc apparatus of claim 29.

With the above configuration, the optimum tilt value is again set in thedisc apparatus. When the track jump of the optical pickup device on themedium is not performed, the numeric value other than the referencevalue of the tilt value is again set as the optimum tilt value in thedisc apparatus and, therefore, the tilt adjustment of the objective lensfor the medium is favorably performed.

In the disc apparatus according to one embodiment of the presentinvention, the above respective disc apparatuses adjusting the detrackvalue and the tilt value are combined.

With the above configuration, a disc apparatus can be provided that canset the optimum detrack value and/or the optimum tilt value in additionto the optimum defocus value in a relatively short time.

An optical disc apparatus 1 of FIG. 1 is configured to be able to set adefocus value suitable for performing the focusing servo operation withthe use of a jitter value of a signal obtained from a medium M such asan optical disc M. The optical disc apparatus 1 of FIG. 1 is alsoconfigured to be able to set a detrack value suitable for performing thetracking servo operation with the use of the jitter value of the signalobtained from the medium M such as the optical disc M. The optical discapparatus 1 of FIG. 1 is also configured to be able to set a tilt valuesuitable for performing the tilt operation with the use of the jittervalue of the signal obtained from the medium M such as the optical discM.

As described above, the jitter (jitter) means slight fluctuation anddistortion of a signal, for example. The focus (focus) means a focalpoint or focal spot, for example. The focusing means bringing into focusor coming into focus, for example. The tracking means tracking minutepits (holes, dents), grooves (grooves), wobbles (meanders), etc.,provided on a signal face portion Ms of the optical disc with the use oflight to set a position on a spirally shaped track, for example. The pitmeans a hole or a dent portions, for example. The groove (groove) meansan elongated dent portion, for example. The wobble (wobble) meansmeandering of track on which a data signal such as information isrecorded, for example. The servo (servo) means a mechanism that measuresa state of a control target to be compared with a predeterminedreference value so as to automatically perform correction control, forexample.

In this description, the defocus adjustment means an adjustmentoperation of focusing for an object out of focus, for example. In thisdescription, the detrack adjustment means an adjustment operation ofperforming the positioning on track for the focus that is not positionedon the track of the optical disc, for example. The tilt in the opticaldisc apparatus 1 or an optical pickup device 2 means angle deviationbetween a signal layer Ms of the optical disc M and a light axis La(FIGS. 1, 2, 4A, and 4B) of a laser beam L emitted from a light-emittingelement 3 of the optical pickup device 2 and transmitted through anobjective lens 4, for example.

The medium (media) means a disc, etc., having stored thereon data,information, and signals, for example. The optical pickup device 2included in the optical disc apparatus 1 (FIG. 1) is used to reproduceor record data such as information in the optical disc M. The opticaldisc M may be an optical disc of the “CD” series, an optical disc of the“DVD” (registered trademark) series, an optical disc of the “HD DVD”(registered trademark) series, and an optical disc of the “Blu-ray Disc”(registered trademark) series. “CD” stands for “Compact disc”(trademark). “DVD” stands for “Digital Versatile disc” (registeredtrademark). “HD DVD” stands for “High Definition DVD” (registeredtrademark).

The signal face portion Ms of the optical disc M is provided with asignal portion Mt for storing data in the optical disc M. The signalface portion Ms of the optical disc M is handled as a surface of asubstantially planar signal layer or surface of a substantially planarrecording layer. The signal portion Mt of the optical disc M is formedas a multiplicity of minute pits Mt. When the circular-plate-shapedoptical disc M is viewed from the top, a multiplicity of the minute pitsMt is arranged to form a spiral shape. When the optical disc M is viewedfrom the side of the signal face portion Ms of the optical disc M, thepit Mt line is considered to be in a spiral shape. Since each of thepits Mt is very small, each of the pits Mt is not visible. In FIGS. 1,2, 4A, and 4B, the signal layer Ms and the pits Mt of the optical disc Mare shown with broken lines for convenience. There can be available theoptical disc M provided with, for example, a groove (not shown) capableof having a signal recorded thereon as the signal portion Mt of theoptical disc M instead of the pits Mt.

The disc may be, for example, an optical disc (not shown) provided witha signal surface on both sides of the disc to enable data write/erase ordata rewrite. The disc may be, for example, an optical disc (not shown)provided with a two-layered signal surface to enable data write/erase ordata rewrite. The disc may be, for example, an “HD DVD” optical disc(not shown) provided with a three-layered signal surface to enable datawrite/erase or data rewrite. The disc may be, for example, a “Blu-rayDisc” optical disc (not shown) provided with a four-layered signalsurface to enable data write/erase or data rewrite. The disc may be, forexample, an optical disc (not shown) having a disc label surface wherevarious writing operations can be performed for a label, etc., byapplying the laser beam L. The signal layer Ms of the optical disc M isformed out of, for example, a metal layer such as a thin metal layer.Information and data are recorded on the signal layer Ms formed out of athin metal layer, etc.

The optical disc M is disposed on a turn table (not shown) driven to berotated by a spindle motor (not shown).

The optical pickup device 2 is provided with the light-emitting element3, so-called laser diode 3 emitting a light beam L, which is the laserbeam L, to the optical disc M. For example, the laser diode 3 isconfigured as, for example, a two-wavelength light-emitting element 3capable of emitting the laser beams L with two types of wavelength whichare a first wavelength and a second wavelength different from the firstwavelength. As above, the laser diode 3 is the light-emitting element 3capable of emitting the laser beams L with a plurality of types ofwavelength, for example. In accordance with the design/specification,etc., of the optical disc apparatus 1 and the optical pickup device 2,the laser diode 3 may be, for example, a single-wavelengthlight-emitting element 3 capable of emitting the laser beam L with onetype of wavelength. The laser diode 3 emits the infrared laser beam Lfor CD with a wavelength of substantially 765 to 830 nm (nanometer) anda reference wavelength of substantially 780 nm, for example.Alternatively, the laser diode 3 emits the red laser beam L for DVD witha wavelength of substantially 630 to 685 nm and a reference wavelengthof substantially 635 nm or substantially 650 nm, for example.Alternatively, the laser diode 3 emits the blue-violet laser beam L for“HD DVD” and/or “Blu-ray Disc” with a wavelength of substantially 350 to450 nm and a reference wavelength of about 405 nm, for example.

The laser diode 3 emits, for example, the laser beam L with an outputvalue of 0.2 to 500 mW (milliwatt), specifically, 2 to 400 mW. Forexample, if an output value of the laser beam L is less than 0.2 mW,there becomes insufficient a light amount of the laser beam L uponarrival at a photodetector 5 after being applied to and reflected by theoptical disc M. When reproducing the data, etc. of the optical disc M,the laser beam L with an output value of several to several tens mW issufficient, for example, about 2 to 20 mW. When writing the data, etc.onto the optical disc M, the laser beam L with an output value ofseveral tens to several hundreds mW is needed. For example, when writingthe data, etc. onto the optical disc M at high speed, the pulse laserbeam L with a high output value such as 400 mW or 500 mW may be needed.

For example, the infrared laser beam for CD is defined as afirst-wavelength laser beam. For example, the red laser beam for DVD isdefined as a second-wavelength laser beam. For example, the blue-violetlaser beam for “HD DVD” and/or “Blu-ray Disc” is defined as athird-wavelength laser beam. The definitions of the laser beams withvarious wavelengths such as the first-wavelength laser beam, thesecond-wavelength laser beam, and the third-wavelength laser beam inthis description are definitions for convenience for explaining theoptical disc apparatus 1 and the optical pickup device 2.

The optical pickup device 2 is provided with a diffraction grating (notshown) substantially rectangular in top view to branch the one laserbeam L emitted from the laser diode 3 into at least three light fluxes(not shown). The laser beam branched by diffraction on the diffractiongrating (not shown) is divided into at least three beams, which are amain beam (zero-order light) and a pair of sub-beams (±first-orderdiffracted light fluxes) branched around the main beam serving as acenter axis, for example. The diffraction grating not shown ispositioned directly behind the laser beam emitting side of the laserdiode 3, for example. For example, the optical pickup device 2 isprovided with, for example, a four-split type diffraction gratingincluding four substantially rectangular diffraction areas formed asperiodic structure units with four different phases (all not shown). Inaccordance with the design/specification, etc. of the optical discapparatus 1 and the optical pickup device 2, for example, there may beused a three-split type diffraction grating that includes threesubstantially rectangular diffraction areas formed as periodic structureunits having with different phases (all not shown). Alternatively, forexample, there may be used a two-split type diffraction grating thatincludes two substantially rectangular diffraction areas formed asperiodic structure units having two different phases (all not shown). Asabove, the optical pickup device 2 is provided with a so-called inlinegrating that is a two or more-split type diffraction grating including aplurality of substantially rectangular diffraction areas. In accordancewith the design/specification, etc. of the optical disc apparatus 1 andthe optical pickup device 2, the optical pickup device 2 may be providedwith, for example, a diffraction grating including one substantiallyrectangular diffraction area formed as one periodic structure unit (allnot shown).

The optical pickup device 2 is provided with the objective lens 4condensing the light beam L emitted from the laser diode 3 to be appliedto the signal face portion Ms of the optical disc M. Since the objectivelens 4 condenses the light beam L, a condensed light spot Ls is appliedto be formed on the signal face portion Ms of the optical disc M.Although the optical disc apparatus 1 is provided with the opticalpickup device 2 with the one objective lens 4 here for convenience, theoptical disc apparatus 1 may be provided with the optical pickup device2 with, for example, the two or more objective lenses 4 in accordancewith the design/specification, etc. of the optical disc apparatus 1 andthe optical pickup device 2. As above, the optical disc apparatus 1 maybe provided with the optical pickup device 2 with a plurality of theobjective lenses 4.

The optical pickup device 2 is provided with the photodetector 5receiving the light beam L reflected from the signal face portion Ms ofthe optical disc M. The photodetector 5 includes at least threelight-receiving units, which are a main light-receiving unit (not shown)substantially rectangular in top view corresponding to the main beam(zeroth-order light) having passed through the diffraction grating notshown and a pair of sub-light-receiving units (not shown) substantiallyrectangular in top view corresponding to a pair of the sub-beams(±first-order diffracted light fluxes) branched by diffraction onpassage through the diffraction grating not shown. The mainlight-receiving unit not shown substantially rectangular in top view issubstantially evenly divided into four parts to include four segmentssubstantially rectangular in top view. The sub-light-receiving unit notshown substantially rectangular in top view is substantially evenlydivided into four parts to include four segments substantiallyrectangular in top view. In accordance with the design/specification,etc. of the optical disc apparatus 1 and the optical pickup device 2,for example, the photodetector 5 may include a light-receiving unit (notshown) substantially rectangular in top view, which is substantiallyevenly divided into two parts to include two segments substantiallyrectangular in top view. As above, the optical pickup device 2 isprovided with the photodetector 5 with the two or more-split typelight-receiving units including a plurality of the segmentssubstantially rectangular in top view. The photodetector 5 is used forreceiving the laser beam L reflected from the signal face portion Ms ofthe optical disc M to be changed into an electric signal so that theinformation recorded on the signal face portion Ms of the optical disc Mis detected. The photodetector 5 is also used for receiving the laserbeam L reflected from the signal face portion Ms of the optical disc Mto be changed into an electric signal so that a servo mechanism (notshown) of a lens holder (not shown) with the objective lens 4 making upthe optical pickup device 2 is operated. When the optical pickup device2 reads the data/information/signals recorded in the optical disc M orwrites the data/information/signals onto the optical disc M, the laserbeams L are applied to the light-receiving units of the photodetector 5to detect the main information signal of the optical disc M and thefocusing error signal and the racking error signal for the optical discM.

The optical pickup device 2 includes a focusing coil 71 that displacingthe objective lens 4 substantially in the direction Df orthogonal to asurface Mf of the optical disc M, a tracking coil 72 displacing theobjective lens 4 substantially in the radial direction Dt of the opticaldisc M, and a tilt coil 73 (FIG. 1) that tilts the objective lens 4 inaccordance with the tilting wobbling of the optical disc M occurringwhen the optical disc M (FIG. 2) is rotating and that tilts theobjective lens 4 in accordance with the lateral wobbling of the opticaldisc M substantially in the radial direction Dt of the optical disc Mgenerated when the optical disc M (FIGS. 4A and 4B) is rotating. Forexample, the optical pickup device 2 is provided with one or a pluralityof, or a plurality of pairs of, i.e. a pair or two or more pairs of, thefocusing coils 71. The focusing coil 71 is defined as a first coil 71,for example. For example, the optical pickup device 2 is provided withone or a plurality of, or a plurality of pairs of, i.e. a pair of or twoor more pairs of, the tracking coils 72. The tracking coil 72 is definedas a second coil 72, for example. For example, the optical pickup device2 is provided with one or a plurality of, or a plurality of pairs of,i.e. a pair of or two or more pairs of, the tilt coils 73. The tilt coil73 is defined as third coil 73, for example. The definitions of thedirections Df, Dt, etc. such as the focusing direction Df or thetracking direction Dt in this description are definitions forconvenience for explaining the optical disc apparatus 1 and the opticalpickup device 2.

The optical pickup device 2 includes a driving device, so-calledactuator, capable of driving the lens holder not shown provided with theobjective lens 4. The “actuator” means a driving device that convertsenergy into a translation motion or rotary motion, etc., for example.The actuator making up the optical pickup device 2 includes: the coils71, 72, 73; the lens holder not shown provided with the coils 71, 72,73, and the objective lens 4; magnetic members (not shown) such asmagnets corresponding and adjacent to the coils 71, 72, 73; a frame yoke(not shown) provided with the magnets not shown and having a yoke (notshown); a suspension wire (not shown) elastically supporting the lensholder not shown; and a circuit substrate (not shown) connected andattached with the suspension wire not shown in a conductive manner.

The “yoke” means an object that structurally supports a magneticcoupling, for example. The “yoke” is considered to reduce leakage ofmagnetic force generated by magnetic members such as magnets and magnetsteels. The “frame” means a frame, a frame work, or a skeletal frame,for example. The frame yoke is formed as a frame including a function ofthe yoke. A circuit board is referred to as PWB (printed wiredboard/printed wiring board), etc., for example. The magnetic fieldsgenerated by the magnets are efficiently utilized by making up theactuator and, for example, the driving forces of the coils 71, 72, 73for the magnets are improved in the actuator.

By supplying electricity to the first coil 71 (FIG. 1) adjacent to themagnet, the lens holder including at least the objective lens 4 and thefirst coil 71 is efficiently driven substantially in the focusingdirection PDF (FIG. 2). By supplying electricity to the second coil 72(FIG. 1) adjacent to the magnet, the lens holder including at least theobjective lens 4 and the second coil 72 is efficiently drivensubstantially in the tracking direction Dt (FIGS. 4A and 4B). Bysupplying electricity to the third coil 73 (FIG. 1) adjacent to themagnet, the lens holder including at least the objective lens 4 and thethird coil 73 is efficiently driven to be tilted (FIGS. 2, 4A, and 4B).

When reading/writing data/information/signals from/onto the optical discM (FIG. 1), the optical pickup device 2 of the optical disc apparatus 1is moved substantially in an inward/outward direction Db of the rotatingoptical disc M. When the focusing adjustment of the objective lens 4 ofthe optical pickup device 2 is performed for the rotating optical discM, normally, the objective lens 4 is slightly moved substantially in adisc vertical direction Da to adjust the position of the objective lens4. The disc vertical direction Da means, for example, a directionperpendicular to the disc surface Mf formed from an inner circumferenceportion Mc to an outer circumference portion Md of the optical disc Mwhen the optical disc M is held in a substantially horizontal state. Thedisc surface Mf of the optical disc M is formed substantially parallelto the signal face portion Ms of the optical disc M.

Specifically describing the state of performing the focusing adjustmentof the objective lens 4 for the optical disc M, the objective lens 4 isslightly moved substantially in an upward direction Da₂ or downwarddirection Da₁ of the optical disc M (FIG. 2) to focus the spot Ls of thelaser beam having passed through the objective lens 4 on the signalportion Mt of the optical disc M.

When the tracking adjustment of the objective lens 4 of the opticalpickup device 2 is performed for the rotating optical disc M (FIG. 1),normally, the objective lens 4 is slightly moved substantially in thedisc inward/outward direction Db to adjust the position of the objectivelens 4. The disc inward/outward direction Db means, for example, adirection along the disc surface Mf between the inner circumferenceportion Mc and the outer circumference portion Md of the optical disc Mwhen the optical disc M is held in a substantially horizontal state.

Specifically describing the state of performing the tracking adjustmentof the objective lens 4 for the optical disc M, the objective lens 4 isslightly moved substantially in an outward direction Db₂ or inwarddirection Db₁ of the optical disc M (FIGS. 4A and 4B) to position thespot Ls of the laser beam having passed through the objective lens 4 onthe signal portion Mt of the optical disc M.

The definitions of directions such as “up”, “down”, “in”, and “out” inthis description are definitions for convenience for explaining theoptical disc apparatus 1, the optical pickup device 2, and the opticaldisc M.

An optical pickup (optical pickup) is generally abbreviated as “OPU”.Alternatively, a term “optical pickup unit” may be used and abbreviatedas “OPU”. The optical pickup device is abbreviated and used here as“OPU” for convenience. The laser diode (laser diode) is abbreviated asLD. The diffraction grating (grating) is abbreviated as “GRT”. Theobjective lens (objective lens) is abbreviated as “OBL”. Thephotodetector (photo detector/photo diode IC) is abbreviated as “PD” or“PDIC”.

The OPU 2 includes the LD 3, the GRT, the OBL 4, the lens holder, thePDIC 5, the focusing coil 71, the tracking coil 72, the tilt coil 73,the magnetic members, the frame yoke, the suspension wire, and thecircuit board. The OPU 2 is moved substantially in the radial directionDt of the optical disc M by a feed motor (not shown) capable of drivingthe main body of the pickup device. In accordance with thedesign/specification, etc., of the OPU 2, the OPU 2 making up theoptical disc apparatus 1 further includes the feed motor.

The optical disc apparatus 1 includes an optical output signalprocessing circuit 6 that: a signal detected by the PDIC 5 provided inthe OPU 2 is input to; and outputs the signal detected by the PDIC 5 as,for example, an RF signal which is considered to be a high frequencysignal. The RF signal means, for example, a signal obtained byconverting a frequency thereof into a frequency that is substantially ashigh as that of a radio wave. “RF” stands for “radio frequency”.

The signal converted from an optical signal to an electric signal by thePDIC 5 provided in the OPU 2 is input to the optical output signalprocessing circuit 6, so-called front-end processing unit 6. Thefront-end processing unit 6 is configured to generate and output a highfrequency signal such as an RF signal that is a reproduction signal ofthe signal recorded in the optical disc M, the focusing error signal,and the tracking error signal.

The focusing error (focusing error) means that the focus Ls of the lightL condensed by the OBL 4 is displaced in the direction Df substantiallyorthogonal to the signal layer Ms, such as the light axis direction Dfrelative to the pits Mt or groove (not shown) of the optical disc M. Thetracking error (tracking error) means that the focus Ls of the light Lcondensed by the OBL 4 is displaced in the direction Dt substantiallyalong the signal layer Ms, such as the radial direction Dt relative tothe pits Mt or groove (not shown) of the optical disc M.

The optical disc apparatus 1 includes a signal processing circuit 7:that amplifies the high frequency signal obtained by the conversion ofthe signal detected by the photodetector 5 in the optical output signalprocessing circuit 6; and that converts the high frequency analog signalinto a digital signal. Specifically, the optical disc apparatus 1includes an RF signal amplifying/processing circuit 7 that amplifies theRF signal obtained by the conversion of the signal detected by the PDIC5 the front-end processing unit 6 and that converts the RF signal, whichis an analog signal, into a digital signal. Analog (analog) means that astate of matter or system is represented with a continuously variablephysical amount, etc. Digital (digital) means that a state of matter orsystem is represented with a discrete signal such as a digit and acharacter.

The high frequency signal such as the RF signal, which is thereproduction signal generated by the front-end processing unit 6 isinput to the signal processing circuit 7 such as the RF signalamplifying/processing circuit 7. The signal processing circuit 7 such asthe RF signal amplifying/processing circuit 7 amplifies the highfrequency signal such as the RF signal. The signal processing circuit 7such as the RF signal amplifying/processing circuit 7 is configured tooutput the input analog signal as a binarized signal, so-called digitalsignal. The jitter value is preferably detected based on the signaloutput from the signal processing circuit 7 such as the RF signalamplifying/processing circuit 7.

The optical disc apparatus 1 includes a digital signal processingcircuit 8 that demodulates the digital signal output from the signalprocessing circuit 7 such as the RF signal amplifying/processing circuit7. The digital signal output from the signal processing circuit 7 suchas the RF signal amplifying/processing circuit 7 is input to the digitalsignal processing circuit 8. The digital signal processing circuit 8 isconfigured to perform the demodulation operation of various signals.

The optical disc apparatus 1 includes a jitter-value detection circuit 9that detects the jitter value, which is a fluctuation value of a signal,based on the signal read from the optical disc M by the PDIC 5 of theOPU 2 having the OBL 4. Specifically, the optical disc apparatus 1includes the jitter-value detection circuit 9, so-called jittermeasurement circuit 9 that detects the jitter value, which is afluctuation value of a signal, based on the signal obtained from thedigital signal processing circuit 8 through the signal processingcircuit 7 such as the RF signal amplifying/processing circuit 7.

The signal generated in the digital signal processing circuit 8 is inputto the jitter measurement circuit 9. For example, if the optical disc Mis an optical disc of the CD standard, the jitter measurement circuit 9detects a signal with a length of 3T to 11T to detect the jitter value,i.e., a time dependent variation of the frequency of the reproductionsignal based on a reference clock signal. The smaller the jitter valuedetected in the jitter measurement circuit 9 is, the smaller the timedependent variation is so that the reproduction characteristics areconsidered to be good.

When a synchronous signal is detected from the high frequency signalsuch as the RF signal, a time variation of a frequency F is detectedwith the reference clock. The smaller the time variation is in value,the smaller it is the time variation is so that the performance isconsidered to be good. The reference clock is abbreviated and used as areference CLK. When describing the length of the synchronizing system,for example, the length thereof is 3T to 11T in the CD series, thelength thereof is 3T to 11T in some cases and mainly 3T to 14T in theDVD series, the length thereof is 2T to 11T in the “HD DVD” series, andthe length thereof is 2T to 8T in the “Blu-ray Disc” series.

The optical disc apparatus 1 includes a system control circuit 10 that:the signal output from the jitter measurement circuit 9 is input to; andthat controls the optical disc apparatus 1 as a whole. Variouscontrol/operations of the optical disc apparatus 1 and the OPU 2 areexecuted by the system control circuit 10. The system control circuit 10is made up of a microcomputer. A microcomputer (micro computer) means avery small computer.

The system control microcomputer is a CPU, a system controller, amicroprocessor, a microcomputer, etc., and is a controlling unitresponsible for system control of the optical disc apparatus 1 as awhole. “CPU” stands for “Central Processing Unit” and means a centralcomputing device. The functions included in the CPU 10 are implementedvia software, so-called program.

The optical disc apparatus 1 includes a first memory circuit 11 havingstored therein a program for causing the CPU 10 to perform variouscontrols. The functions implemented by software are stored in the firstmemory circuit 11 accessible from the CPU 10. The system control circuit10 is configured to perform various controls/operations based on theprogram stored in the first memory circuit 11 such as a flash ROM. “ROM”stands for “read-only memory”. For example, a flash memory (flashmemory) is used as the first memory circuit 11.

Specifically describing the first memory circuit 11, for example, thefirst memory circuit 11 may be ROM such as EEPROM. ROM means a memoryfor read-only. EEPROM means ROM whose contents can electrically berewritten. EEPROM is a so-called nonvolatile memory. When a change ismade in EEPROM, a voltage higher than a normal voltage is used. InEEPROM, stored information can electrically be erased. “EEPROM” standsfor “Electronically Erasable and Programmable Read Only Memory”.

Alternatively, the first memory circuit 11 may be ROM such as EPROM.EPROM means ROM whose memory contents can be erased/written any numberof times. In EPROM, when memory contents are erased, a particular methodis used that is different from a method used at the time of reading.“EPROM” stands for “Erasable Programmable Read Only Memory”.

The optical disc apparatus 1 includes a second memory circuit 12 wherevarious values input to the CPU 10 can be stored/erased. For example,RAM can be used as the second memory circuit 12. RAM means a storagedevice storing data accessible in substantially the same time regardlessof storage location and order. “RAM” stands for “random access memory”.The system control circuit 10 controls the second memory circuit 12 suchas RAM as to an operation thereof. The second memory circuit 12 isconfigured to be capable of having stored therein a defocus value and ajitter value corresponding to the defocus value. The second memorycircuit 12 is configured to be capable of having stored therein adetrack value and a jitter value corresponding to the detrack value. Thesecond memory circuit 12 is configured to be capable of having storedtherein a tilt value and a jitter value corresponding to the tilt value.The second memory circuit 12 is configured to be capable of havingstored therein at least one or more values selected from a groupconsisting of a defocus value and a jitter value corresponding to thedefocus value, a detrack value and a jitter value corresponding to thedetrack value, and a tilt value and a jitter value corresponding to thetilt value.

Although the second memory circuit 12 is configured to be capable ofhaving stored therein the three forms of (a total of six kinds) valueswhich are a defocus value and a jitter value corresponding to thedefocus value, a detrack value and a jitter value corresponding to thedetrack value, and a tilt value and a jitter value corresponding to thetilt value, in accordance with the design/specification, etc. of theoptical disc apparatus 1, for example, the second memory circuit 12 maybe configured to be capable of having stored therein the two forms of (atotal of four kinds) values which are a defocus value and a jitter valuecorresponding to the defocus value, and a detrack value and a jittervalue corresponding to the detrack value. Alternatively, in accordancewith the design/specification, etc. of the optical disc apparatus 1, forexample, the second memory circuit 12 may be configured to be capable ofhaving stored therein the two forms of (a total of four kinds) valueswhich are a detrack value and a jitter value corresponding to thedetrack value, and a tilt value and a jitter value corresponding to thetilt value. Alternatively, in accordance with the design/specification,etc. of the optical disc apparatus 1, for example, the second memorycircuit 12 may be configured to be capable of having stored therein thetwo forms of (a total of four kinds) values which are a tilt value and ajitter value corresponding to the tilt value, and a defocus value and ajitter value corresponding to the defocus value.

In accordance with the design/specification, etc. of the optical discapparatus 1, for example, the second memory circuit 12 is configured tobe capable of having stored therein a plurality of forms of values to berequired, which are selected from a group consisting of a defocus valueand a jitter value corresponding to the defocus value, a detrack valueand a jitter value corresponding to the detrack value, and a tilt valueand a jitter value corresponding to the tilt value.

The optical disc apparatus 1 includes a defocus-value setting circuit21: that adjusts the defocus value used for moving the OBL 4 in thelight axis direction Df of the OBL 4 when the OBL 4 of the OPU 2 isfocused on the signal face portion Ms of the optical disc M based on thesignal having passed through the jitter measurement circuit 9 and theCPU 10; and that causes a focusing servo circuit 31 to perform thedefocus adjustment based on the defocus value having been adjusted andset.

The optical disc apparatus 1 includes the focusing servo circuit 31 thatenables the focusing servo operation of the lens holder (not shown)including the OBL 4 based on the focusing error signal generated in thefront-end processing unit 6. Specifically, the optical disc apparatus 1includes the focusing servo circuit 31: that the focusing error signalgenerated in the front-end processing unit 6 based on the signaldetected by the PDIC 5 is input to; and that generates a control signalcausing the OBL 4 included in the OPU 2 to be displaced substantially inthe light axis direction Df of the OBL 4, which is a directionorthogonal to the surface Mf of the optical disc M. The focusing errorsignal is generated in the front-end processing unit 6 and then outputfrom the front-end processing unit 6, to be input to the focusing servocircuit 31. The focusing servo circuit 31 is configured with the use ofan equalizer. The focusing servo circuit 31 is configured as a digitalequalizer capable of supporting a digital signal. An equalizer(equalizer) is an electric circuit for processing and adjusting overallfrequency characteristics of a signal such as an audio signal. Anequalizer is abbreviated as “EQ”.

The defocus value for the focusing servo circuit 31 is set by thedefocus-value setting circuit 21. The defocus-value setting circuit 21is configured to be controlled by the system control circuit 10. If theoperation for setting the defocus value suitable for the optical disc(M) is performed in the optical disc apparatus 1 after the optical disc(M) is disposed in the optical disc apparatus 1, the defocus value setfor the focusing servo circuit 31 is changed, for example, in a stepwiseof 2%, from −10% to +10%, or specifically, −8% to +8%, relative to thedefocus value 0 that is a reference value, for example.

In accordance with the design/specification, etc. of the optical discapparatus 1, if the operation for setting the defocus value suitable forthe optical disc (M) is performed in the optical disc apparatus 1 afterthe optical disc (M) is disposed in the optical disc apparatus 1, thedefocus value set for the focusing servo circuit 31 may be changed, forexample, in a stepwise of 1%, from −10% to +10%, or specifically, −8% to+8%, relative to the defocus value 0 that is a reference value, forexample.

The optical disc apparatus 1 includes a detrack-value setting circuit22: that adjusts the detrack value used for moving the OBL 4 in theradial direction Dt of the optical disc M when the OBL 4 of the OPU 2 isfocused on the signal face portion Ms of the optical disc M based on thesignal having passed through the jitter measurement circuit 9 and theCPU 10; and that causes a tracking servo circuit 32 to perform thedetrack adjustment based on the detrack value having been adjusted andset.

The optical disc apparatus 1 includes the tracking servo circuit 32 thatenables the tracking servo operation of the lens holder (not shown)including the OBL 4 based on the tracking error signal generated in thefront-end processing unit 6. Specifically, the optical disc apparatus 1includes the tracking servo circuit 32: that the tracking error signalgenerated in the front-end processing unit 6 based on the signaldetected by the PDIC 5 is input to; and that generates a control signalcausing the OBL 4 including in the OPU 2 to be displaced substantiallyin the radial direction Dt of the optical disc M. The tracking errorsignal is generated in the front-end processing unit 6 and then outputfrom the front-end processing unit 6, to be input to the tracking servocircuit 32. The tracking servo circuit 32 is configured with the use ofan equalizer. The tracking servo circuit 32 is configured as a digitalequalizer capable of supporting a digital signal.

The detrack value for the tracking servo circuit 32 is set by thedetrack-value setting circuit 22. The detrack-value setting circuit 22is configured to be controlled by the system control circuit 10. If theoperation for setting the detrack value suitable for the optical disc(M) is performed in the optical disc apparatus 1 after the optical disc(M) is disposed in the optical disc apparatus 1, the detrack value setfor the tracking servo circuit 32 is changed, for example, in a stepwiseof 2%, from −10% to +10%, or specifically, −8% to +8%, relative to thedetrack value 0 that is a reference value, for example.

In accordance with the design/specification, etc. of the optical discapparatus 1, if the operation for setting the detrack value suitable forthe optical disc (M) is performed in the optical disc apparatus 1 afterthe optical disc (M) is disposed in the optical disc apparatus 1, thedetrack value set for the tracking servo circuit 32 may be changed, forexample, in a stepwise of 1%, from −10% to +10%, or specifically, −8% to+8%, relative to the defocus value 0 that is a reference value, forexample.

The optical disc apparatus 1 includes a tilt-value setting circuit 23:that adjusts the tilt value used for correcting the angular displacementof the OBL 4 relative to the signal face portion Ms of the optical discM when the OBL 4 of the OPU 2 is focused on the signal face portion Msof the optical disc M based on the signal having passed through thejitter measurement circuit 9 and the CPU 10; and that causes the tiltadjustment to be performed based on the tilt value having adjusted andset.

The suitable tilt value is set by the tilt-value setting circuit 23. Thetilt-value setting circuit 23 is configured to be controlled by thesystem control circuit 10. If the operation for setting the tilt valuesuitable for the optical disc (M) is performed in the optical discapparatus 1 after the optical disc (M) is disposed in the optical discapparatus 1, the tilt value to be set is changed, for example, in astepwise of 2%, from −10% to +10%, or specifically, −8% to +8%, relativeto the tilt value 0 that is a reference value, for example.

In accordance with the design/specification, etc. of the optical discapparatus 1, if the operation for setting the tilt value suitable forthe optical disc (M) is performed in the optical disc apparatus 1 afterthe optical disc (M) is disposed in the optical disc apparatus 1, thetilt value to be set may be changed, for example, in a stepwise of 1%,from −10% to +10%, or specifically, −8% to +8%, relative to the tiltvalue 0 that is a reference value, for example.

The optical disc apparatus 1 includes a focusing tilt band-pass filtercircuit 41 (FIG. 1) that a focusing control signal FDO output from, forexample, the focusing servo circuit 31 is input to; and that extracts asignal corresponding to a rotation period Cf (FIG. 3) of the opticaldisc M based on the focusing control signal FDO. The FDO stands for“focus drive out” in this description. The band-pass filter (band passfilter) is abbreviated as “BPF”. The BPF means a filter that only allowsa frequency signal within a predetermined range to be passedtherethrough and that attenuates a signal other than the frequencysignal within the predetermined range. If wobbling occurs in the opticaldisc M (FIG. 2) at the time of reproducing from the disc or recordinginto the disc, the wobbling component becomes the FDO signal (FIG. 3).The focusing servo operation is executed by the application of the FDOsignal.

The optical disc apparatus 1 (FIG. 1) includes a tracking tilt band-passfilter circuit 42 (FIG. 1) that a tracking control signal TDO outputfrom, for example, the tracking servo circuit 32 is input to; and thatextracts a signal corresponding to a rotation period Ct (FIG. 5) of theoptical disc M based on the tracking control signal TDO. The TDO standsfor “tracking drive out” in this description. If eccentricity occurs inthe optical disc M (FIG. 4) at the time of reproducing from the disc orrecording into the disc, the eccentricity component becomes the TDOsignal (FIG. 5). The tracking servo operation is executed by theapplication of the TDO signal.

In accordance with the design/specification, etc. of the optical discapparatus 1 and the optical pickup device 2, for example, the opticaldisc apparatus 1 is also usable if the focusing tilt band-pass filtercircuit 41, the tracking tilt band-pass filter circuit 42, etc. areomitted without being provided.

The optical disc apparatus 1 includes a focusing tilt signal adjustmentcircuit 51 that causes the tilt adjustment to be performed for the OBL 4as to the angular displacement based on the jitter detected by thejitter measurement circuit 9 when the angular displacement relative tothe signal face portion Ms of the optical disc M is caused to occur inthe OBL 4 of the OPU 2. The focusing tilt signal adjustment circuit 51is capable of adjusting the level of the signal extracted in thefocusing tilt band-pass filter circuit 41. For example, an amp is usedfor the focusing tilt signal adjustment circuit 51. The amp stands foran amplifier (amplifier) and means amplification equipment.

The optical disc apparatus 1 includes a tracking tilt signal adjustmentcircuit 52 that causes the tilt adjustment to be performed for the OBL 4as to the angular displacement based on the jitter detected by thejitter measurement circuit 9 when the angular displacement relative tothe signal face portion Ms of the optical disc M is caused to occur inthe OBL 4 of the OPU 2. The tracking tilt signal adjustment circuit 52is capable of adjusting the level of the signal extracted by thetracking tilt band-pass filter circuit 42. For example, an amp is usedfor the tracking tilt signal adjustment circuit 52.

The optical disc apparatus 1 includes an addition circuit 53 that adds atilt-value setting adjustment signal output from the tilt-valueadjustment circuit 23 to the tilt adjustment signal output from the tiltsignal adjustment circuits 51, 52. Specifically, the optical discapparatus 1 includes the addition circuit 53 that adds the focusing tiltadjustment signal output from the focusing tilt signal adjustmentcircuit 51, the tracking tilt adjustment signal output from the trackingtilt signal adjustment circuit 52, and the tilt-value setting adjustmentsignal output from the tilt-value adjustment circuit 23. The focusingtilt adjustment signal is output from the focusing tilt signaladjustment circuit 51. The tracking tilt adjustment signal is outputfrom the tracking tilt signal adjustment circuit 52. The tilt-valuesetting adjustment signal set to the suitable tilt value is output fromthe tilt-value adjustment circuit 23. The signal is added by theaddition circuit 53.

The optical disc apparatus 1 includes a focusing coil drive circuit 61:that the focusing control signal output from the focusing servo circuit31 is input to; and that supplies a drive signal to the focusing coil 71included in the OPU 2. The focusing servo circuit 31 outputs to thefocusing coil drive circuit 61 the focusing control signal for reducingthe level of the focusing error signal based on the input focusing errorsignal. The focusing control signal output from the focusing servocircuit 31 is input to the focusing coil drive circuit 61. The focusingcoil drive circuit 61 supplies the focusing coil drive signal to thefocusing coil 71. When the focus of the laser beam L condensed by theOBL 4 is caused to be displaced in the focusing direction Df of the OBL4 relative to the pits Mt of the optical disc M, the focusing drivesignal is sent from the focusing coil drive circuit 61 to the focusingcoil 71 of the OPU 2 to perform the focusing adjustment of the OBL 4 ofthe OPU 2. The drive circuit is referred to as a driver, etc.

The optical disc apparatus 1 includes a tracking coil drive circuit 62that the tracking control signal output from the tracking servo circuit32 is input to, and that supplies a drive signal to the tracking coil 72included in the OPU 2. The tracking servo circuit 32 outputs to thetracking coil drive circuit 62 the tracking control signal for reducingthe level of the tracking error signal based on the input tracking errorsignal. The tracking control signal output from the tracking servocircuit 32 is input to the tracking coil drive circuit 62. The trackingcoil drive circuit 62 supplies the tracking coil drive signal to thetracking coil 72. When the focus of the laser beam L condensed by theOBL 4 is caused to be displaced in the tracking direction Df of the OBL4 relative to the pits Mt of the optical disc M, the tracking drivesignal is sent from the tracking coil drive circuit 62 to the trackingcoil 72 of the OPU 2 to perform the tracking adjustment of the OBL 4 ofthe OPU 2.

The optical disc apparatus 1 includes a tilt coil drive circuit 63 thatthe addition signal output from the addition circuit 53 is input to.Specifically, the optical disc apparatus 1 includes the tilt coil drivecircuit 63 that the tilt control signal output from the addition circuit53 is input to, and that supplies a drive signal to the tilt coil 73included in the OPU 2. There is generated in the tilt coil drive circuit63 the drive signal to be sent to the tilt coil 73 of the OPU 2 based onthe addition signal generated in the addition circuit 53 to perform thetilt adjustment of the angle of the OBL 4 of the OPU 2. The tilt coildrive circuit 63 supplies the tilt coil drive signal to the tilt coil73. When the focus of the laser beam L condensed by the OBL 4 is causedto be displaced relative to the pits Mt of the optical disc M, the tiltdrive signal is sent from the tilt coil drive circuit 63 to the tiltcoil 73 of the OPU 2 to perform the tilt adjustment of the OBL 4 of theOPU 2.

As shown in FIG. 1, the optical disc apparatus 1 includes at least oneor more setting circuits 21, 22, 23 among the setting circuits 21, 22,23 to be selected from a group consisting of the defocus-value settingcircuit 21, the detrack-value setting circuit 22, and the tilt-valuesetting circuit 23. Therefore, the optical disc apparatus 1 isconfigured to be capable of setting at least one or more optimum valuesamong the optimum defocus value, the optimum detrack value, and theoptimum tilt value.

Specifically, the optical disc apparatus 1 of FIG. 1 includes the OPU 2,the optical output signal processing circuit 6, the signal processingcircuit 7, the digital signal processing circuit 8, the jitter-valuedetection circuit 9, the system control circuit 10, the first memorycircuit 11, the second memory circuit 12, the defocus-value settingcircuit 21, the detrack-value setting circuit 22, the tilt-value settingcircuit 23, the focusing servo circuit 31, the tracking servo circuit32, the focusing tilt band-pass filter circuit 41, the tracking tiltband-pass filter circuit 42, the focusing tilt signal adjustment circuit51, the tracking tilt signal adjustment circuit 52, the addition circuit53, the focusing coil drive circuit 61, the tracking coil drive circuit62, and the tilt coil drive circuit 63. A lens adjustment circuit of theoptical disc apparatus 1 is configured as above.

In accordance with the design/specification, etc. of the optical discapparatus 1, for example, the OPU 2 and the optical disc apparatus 1 arealso usable in which the focusing coil 71 and/or the tracking coil 72 ofthe OPU 2 also serves as the tilt coil 73 of the OPU 2. Specifically,the OPU 2 and the optical disc apparatus 1 are also usable in which thefocusing coil 71 and/or the tracking coil 72 of the OPU 2 are configuredas the coil 71/72 also capable of performing the tilt adjustment, byconnecting a conductor extended from the tilt coil drive circuit 63 ofthe optical disc apparatus 1 to, for example, the focusing coil 71and/or the tracking coil 72 of the OPU 2 in a conductive manner withoutproviding the tilt coil 73 exclusively for the tilt adjustment on theOPU 2. More specifically, the focusing coil 71 of the OPU 2 may beconfigured to also serve as the tilt coil 73 of the OPU 2 by connectinga conductor extended from the tilt coil drive circuit 63 of the opticaldisc apparatus 1 to, for example, the focusing coil 71 of the OPU 2 in aconductive manner without providing the tilt coil 73 exclusively for thetilt adjustment in the OPU 2, so that the focusing coil 71 is configuredas, for example, the focus/tilt coil 71 that functions at the time ofthe focusing adjustment and/or the tilt adjustment.

The optical disc apparatus 1 includes a digital signal processing deviceincluding, for example, the digital signal processing circuit 8, whichis so-called digital signal processor. The digital signal processormeans a microprocessor specialized mainly in digital signal processing,for example. The digital signal processor (digital signal processor) isabbreviated as “DSP”. A chip including the digital signal processingcircuit 8 making up the DSP is provided. Since the DSP including thedigital signal processing circuit 8 is used, high-speed calculationprocessing can be executed by the CPU 10, etc., for example. By usingthe DSP, for example, since an SN (signal/noise) ratio becomessubstantially 90 db (decibel) or more when executing signal processing,the effect of noise can easily be avoided and the effect of ambientatmospheric temperature can also easily be restrained. Therefore, highlyaccurate calculation processing, etc., is executed at high speed byusing the DSP.

For example, the DSP of the optical disc apparatus 1 includes thedigital signal processing circuit 8, the jitter-value detection circuit9, the system control circuit 10, the defocus-value setting circuit 21,the detrack-value setting circuit 22, the tilt-value setting circuit 23,the focusing servo circuit 31, and the tracking servo circuit 32. Forexample, a chip obtained by integrating complicated circuits into onepackage is configured with the optical output signal processing circuit6, the signal processing circuit 7, the digital signal processingcircuit 8, the jitter-value detection circuit 9, the system controlcircuit 10, the first memory circuit 11, the second memory circuit 12,the defocus-value setting circuit 21, the detrack-value setting circuit22, the tilt-value setting circuit 23, the focusing servo circuit 31,the tracking servo circuit 32, the focusing tilt band-pass filtercircuit 41, and the tracking tilt band-pass filter circuit 42.

There is made up the optical disc apparatus 1 capable of setting theoptimum defocus value by making up the optical disc apparatus 1 shown inFIG. 1. The optimum defocus value is set in the optical disc apparatus 1in accordance with the jitter value detected based on the signal readfrom the optical disc M and the defocus value based on the detectedjitter value.

There is made up the optical disc apparatus 1 capable of setting theoptimum detrack value by making up the optical disc apparatus 1 shown inFIG. 1. The optimum detrack value is set in the optical disc apparatus 1in accordance with the jitter value detected based on the signal readfrom the optical disc M and the detrack value based on the detectedjitter value.

There is made up the optical disc apparatus 1 capable of setting theoptimum tilt value by making up the optical disc apparatus 1 shown inFIG. 1. The optimum tilt value is set in the optical disc apparatus 1 inaccordance with the jitter value detected based on the signal read fromthe optical disc M and the tilt value based on the detected jittervalue.

After the optical disc M is disposed in the optical disc apparatus 1,the signal is read from the optical disc M and the jitter value isdetected so that the defocus adjustment of the OBL 4 for the opticaldisc M is performed. The above defocus adjustment is performed withinsubstantially 20 seconds.

Since the time spent on the defocus-value adjusting method of theoptical disc apparatus 1 is set to a short time, the defocus adjustmentis performed in the optical disc apparatus 1 without waiting for a longtime due to the defocus adjustment. Since the defocus adjustment isperformed within substantially 20 seconds when performing the defocusadjustment of the OBL 4 for the optical disc M, a situation is avoidedwhere one must wait for a very long time due to the defocus adjustmentautomatically performed by the optical disc apparatus 1 from the timewhen the optical disc M is disposed in the optical disc apparatus 1 tothe time when the signal such as data/information is started to be readfrom the optical disc M.

When the detrack adjustment of the OBL 4 is performed for the opticaldisc M by reading the signal from the optical disc M and detecting thejitter value after the optical disc M is disposed in the optical discapparatus 1, the detrack adjustment is performed within substantially 20seconds.

Since the time spent on the detrack-value adjusting method of theoptical disc apparatus 1 is set to a short time, the detrack adjustmentis performed in the optical disc apparatus 1 without waiting for a longtime due to the detrack adjustment. Since the detrack adjustment isperformed within substantially 20 seconds when performing the detrackadjustment of the OBL 4 for the optical disc M, a situation is avoidedwhere one must wait for a very long time due to the detrack adjustmentautomatically performed by the optical disc apparatus 1 from the timewhen the optical disc M is disposed in the optical disc apparatus 1 tothe time when the signal such as data/information is started to be readfrom the optical disc M.

When the tilt adjustment of the OBL 4 is performed for the optical discM by reading the signal from the optical disc M and detecting the jittervalue after the optical disc M is disposed in the optical disc apparatus1, the tilt adjustment is performed within substantially 20 seconds.

Since the time spent on the tilt-value adjusting method of the opticaldisc apparatus 1 is set to a short time, the tilt adjustment isperformed in the optical disc apparatus 1 without waiting for a longtime due to the tilt adjustment. Since the tilt adjustment is performedwithin substantially 20 seconds when performing the tilt adjustment ofthe OBL 4 for the optical disc M, a situation is avoided where one mustwait for a very long time due to the tilt adjustment automaticallyperformed by the optical disc apparatus 1 from the time when the opticaldisc M is disposed in the optical disc apparatus 1 to the time when thesignal such as data/information is started to be read from the opticaldisc M.

Although the optical disc apparatus 1 includes the three settingcircuits 21, 22, and 23, which are the defocus-value setting circuit 21,the detrack-value setting circuit 22, and the tilt-value setting circuit23, the optical disc apparatus 1 may be configured to include, forexample, the defocus-value setting circuit 21 and the detrack-valuesetting circuit 22 in accordance with the design/specification, etc. ofthe optical disc apparatus 1. The optical disc apparatus 1 may beconfigured to include, for example, the detrack-value setting circuit 22and the tilt-value setting circuit 23, in accordance with thedesign/specification, etc. of the optical disc apparatus 1. The opticaldisc apparatus 1 may be configured to include, for example, thetilt-value setting circuit 23 and the defocus-value setting circuit 21in accordance with the design/specification, etc. of the optical discapparatus 1.

In accordance with the design/specification, etc. of the optical discapparatus 1, for example, the optical disc apparatus 1 may be configuredto include a plurality of the required setting circuits 21 and/or 22and/or 23 among the setting circuits 21, 22, 23 selected from a groupconsisting of the defocus-value setting circuit 21, the detrack-valuesetting circuit 22, and the tilt-value setting circuit 23.

When performing the adjusting method of the optical disc apparatus 1,the optical disc apparatus 1 including the OPU 2 with the OBL 4 is usedto detect the jitter value of the signal read from the optical disc Mand to adjust the position of the OBL 4 for the optical disc M based onthe detected jitter value.

The defocus-value adjusting method of the optical disc apparatus 1 willthen be described.

The defocus-value adjusting method of the optical disc apparatus 1 willbe described with reference to the figures in conjunction withflowcharts shown in FIGS. 6A, 6B, and 7.

The defocus adjusting method of the optical disc apparatus 1 based onthe jitter value is performed as follows. The offset adjustment of thefocus is performed at the time of initial data reading or immediatelyafter the initial data reading of the OPU 2 in the vicinity of the discinner circumferential portion Mc immediately before performing the datareproduction of the reproduction/recording optical disc M (FIG. 1), forexample. At this time, there are performed the defocus-value adjustmentprocess, etc. corresponding to a reference voltage value (Vref), forexample. For example, in the optical disc apparatus 1, there is read asignal having the shape of S-curve substantially laid sideways with −50%to +50% of the defocus values centering a reference value 0, which isthe reference voltage value (Vref).

The optical disc apparatus 1 is used to perform the focusing adjustmentof the OBL 4 for the signal face portion Ms of the optical disc M. Theoptical disc apparatus 1 is used to perform the defocus-value adjustingmethod in the optical disc apparatus 1.

For example, when the optical disc apparatus 1 is turned on,preparations are started for performing the defocus-value adjustingmethod of the optical disc apparatus 1. When the optical disc apparatus1 is turned on and the optical disc apparatus 1 is rendered in thepower-on state, for example, data such as various pieces of informationare sent from the memory circuit 11 such as the ROM 11 to the systemcontrol circuit 10. At this point, various data, for example, apredetermined jitter value, jitter(i_(a)f), and a determination value,jitter (i_(a)s), are sent to the system control circuit 10 and set inthe system control circuit 10 (FIG. 6A: S110).

The defocus-value adjusting method of this optical disc apparatus 1(FIG. 1) is a defocus-value adjusting method of the optical discapparatus 1 that performs the focusing adjustment of the OBL 4 for theoptical disc M with the use of the optical disc apparatus 1 includingthe OPU 2 having the OBL 4 by detecting the jitter value of the signalread from the optical disc M and by adjusting the defocus value used formoving the OBL 4 in the light axis direction Df of the OBL 4 when theOBL 4 of the OPU 2 is focused on the signal face portion Ms of theoptical disc M based on the detected jitter value. The defocus-valuesetting process is performed as follows.

By disposing the optical disc M in the optical disc apparatus 1, theoperation is substantially started for setting the suitable defocusvalue in the optical disc apparatus 1. First, focus bias, so-calleddefocus is applied to the focusing coil (FOCUSING COIL) 71 to measurethe jitter with the use of the optical disc apparatus 1. When causingthe optical disc apparatus 1 to perform the defocus-value adjustingmethod, the jitter is first detected/measured at the defocus value of ±0(FIG. 6A: S120). At this point, for example, as shown in FIG. 11 or FIG.12, if it is determined that the jitter value jitter(i_(a)o) at thedefocus value of ±0 is a small value equal to or smaller than aspecified value jitter(i_(a)f) and the program in the CPU 10 determinesthat the optical disc M (FIG. 1) has good jitter characteristics (FIG.6A, S130: NO), the defocus value is set to zero (FIG. 6A: S180) and thedefocus adjustment is completed.

This optical disc apparatus 1 (FIG. 1) performs a differentdefocus-value adjusting method for each of the optical disc M with goodjitter characteristics and the optical disc (M) presumed/determined tohave the jitter characteristics that are not good and requiring thedetection/check of jitter values. In this description, for example,presence or absence of parentheses ( ) for the character M is used todifferentiate between the optical disc M with good jittercharacteristics and the optical disc (M) presumed/determined to have thejitter characteristics that are not good and requiring thedetection/check of jitter values.

When the defocus-value adjusting method in the optical disc apparatus 1is performed with the use of the optical disc apparatus 1, for example,as shown in FIGS. 8, 9, and 10, jitter values are detected/measured asneeded. Specifically, in the case of the optical disc (M) for which: itis determined that the jitter value jitter (i_(a)o) at the defocus valueof ±0 is a value greater than the specified value jitter (i_(a)f); theprogram in the CPU 10 (FIG. 1) presumes/determines that the jittercharacteristics are not good; and that each of the jitter valuesrequires the detection/check, the following measurement is performed.First, when reading the signal from the optical disc (M) to detect thejitter value, the defocus value within a predetermined range is changed.Specifically, when reading the signal from the optical disc (M) todetect the jitter value, the defocus value is changed stepwise within apredetermined range of numeric values including the reference value 0 ofthe defocus value (FIGS. 8, 9, and 10) being centered (FIG. 6A: S140,FIG. 6B: S141 to S146). Every time the defocus value is changedstepwise, the jitter value is detected.

The operation of setting the defocus value is performed by thedefocus-value setting circuit 21 in the state of performing thereproduction operation for the signal recorded in the optical disc (M)(FIG. 1). In the defocus-value setting circuit 21, a value of thedefocus value set for the focusing servo circuit 31 is changed in astepwise of 2% from −8% to +8% relative to the reference value 0 (FIGS.8, 9, and 10). At the same time, the jitter value of the reproductionsignal is detected correspondingly to the defocus values by the jittermeasurement circuit 9 to set the defocus value.

Specifically, while the defocus value for the focusing servo circuit 31is set by the defocus-value setting circuit 21 to a value lower than thereference value 0 by about −8%, the reproduction operation is performedfor the signal recorded in the optical disc (M) to detect the jittervalue included in the reproduction signal with the jitter measurementcircuit 9. The jitter value detected in this way is stored in the memorycircuit 12 such as the RAM 12 along with the defocus value.

The defocus value is changed in a stepwise of 2% from −8% to +8%relative to the reference value 0, the jitter value corresponding to thedefocus value is detected, and the jitter value is stored in the memorycircuit 12 along with the defocus value. The above operations arerepeatedly performed.

When the operation is started for setting the defocus value in theoptical disc apparatus 1, in the case of the optical disc (M) for whichit is determined that the jitter values require detection/check duringthe process of the defocus adjusting method of the optical discapparatus 1, the operation of detecting the jitter value is firstperformed every time the defocus value is changed within a predeterminedrange (FIG. 6A: S140, FIG. 6B: S141 to S146). The predetermined range isdefined, for example, if the defocus value 0 is defined as a referencevalue, as the defocus values from −10% to +10% to be set for thefocusing servo circuit 31 relative to the reference value (FIGS. 8, 9,and 10). The preferable predetermined range of defocus values isdefined, for example, if the defocus value 0 is defined as a referencevalue, as a range from −8% to +8% to be set for the focusing servocircuit 31 relative to the reference value.

For example, if the defocus value is set to a value smaller than the−10% value, the focusing servo function may not work normally.Alternatively, for example, if the defocus value is set to a valuegreater than the +10% value, the focusing servo function may not worknormally. Therefore, the defocus values from −10% to +10% centering thereference value 0 of the defocus value may be set for the focusing servocircuit 31. Preferably, the focusing servo function works normally bysetting the defocus values from −8% to +8% centering the reference value0 of the defocus value for the focusing servo circuit 31.

For example, in the case of the optical disc (M) (FIG. 1) for which: itis determined that the jitter value jitter(i_(a)o) at the referencevalue 0 of the defocus value (FIGS. 8, 9, and 10) is a value greaterthan the specified value jitter(i_(a)f); it is presumed/determined thatthe jitter value is not good; and it is also determined that each of thejitter values requires the detection/check, the following process isperformed under the control of the program in the CPU 10. The followingprocess is performed by the CPU 10 and the second memory circuit 12.

First, an initial value is set by the program in the CPU 10 to seti_(a)=−4 (FIG. 6B: S141). For example, a value of “DEFOCUS=2%×i_(a)” isset (SET) to “FOCUS_BIAS” (S142). The jitter value is measured by theOPU 2 (S143) and the result is stored in the second memory circuit 12 as“jitter (i_(a))” (S144).

The “i_(a)” is incremented by the program in the CPU 10 (S141, S142 toS146). Increment (increment) means to increase a numeric value by agiven value when repetitive processing, etc. are executed inprogramming.

In the case of “i_(a)<5” (S146: NO), a value of “DEFOCUS=2%×i_(a)” isset to “FOCUS_BIAS” (S142) and the jitter is measured again by the OPU 2(S143) to store the result in the second memory circuit 12 as“jitter(i_(a))” (S144). In the case of “i_(a)≧5” (S146: YES), a minimumvalue is obtained from “jitter(i_(a))”, and “i_(a)” at this point isdefined as “i_(a)min” (FIG. 6A: S150). In the case of “i_(a)≧5” (FIG.6B, S146: YES), a maximum value is obtained from “jitter(i_(a))”, and“i_(a)” at this point is defined as “i_(a)max” (FIG. 6A: S150).

The optimum defocus value is then set based on a difference valuejitter(i_(a)d) between the maximum jitter value jitter(i_(a)max) and theminimum jitter value jitter(i_(a)min) of the detected jitter values(S160).

The defocus value is changed within the predetermined range: thedetection operation of the jitter values is performed (FIG. 6A: S140,FIG. 6B: S141 to S146); and the maximum jitter value jitter(i_(a)max)and the minimum jitter value jitter(i_(a)min) are selected from thedetected jitter values (FIG. 6A: S150).

After performing the selection setting operation at the step of S150,there is performed a determination operation which determines whether[jitter(i_(a)max)−jitter(i_(a)min)>jitter(i_(a)s)] is satisfied (S160:YES) or [jitter(i_(a)max)−jitter(i_(a)min)>jitter(i_(a)s)] is notsatisfied (S160: NO). If it is determined that[jitter(i_(a)max)−jitter(i_(a)min)>jitter(i_(a)s)] is satisfied at thestep of S160 (S160: YES), the defocus value corresponding to the minimumjitter value jitter(i_(a)min) is set as the optimum defocus value(S170). Alternatively, if it is determined that[jitter(i_(a)max)−jitter(i_(a)min)>jitter(i_(a)s)] is not satisfied atthe step of S160 (S160: NO), the reference value 0 of the defocus valueis set as the optimum defocus value (S180).

The optimum defocus value is set in the optical disc apparatus 1 byperforming the defocus-value adjusting method of the optical discapparatus 1 as above. The jitter value is detected as needed every timethe defocus value is changed stepwise within the predetermined range ofnumeric values including the reference value 0 of the defocus valuebeing centered, so that the optimum defocus value is set based on thedifference value jitter(i_(a)d) between the maximum jitter valuejitter(i_(a)max) and the minimum jitter value jitter(i_(a)min) of thedetected jitter values. Therefore, the optimum defocus value is set inthe optical disc apparatus 1. Since the optimum defocus value is set inthe optical disc apparatus 1, the OPU 2 performs the stable focusingservo operation for the optical disc M. The defocus value settingoperation can easily be performed in the optical disc apparatus 1.

After the optical disc (M) is completely disposed in the optical discapparatus 1, when reading each of the signals from the optical disc (M)and detecting each of the jitter values to perform the defocusadjustment of the OBL 4 for the optical disc (M), the defocus adjustmentis performed within a time period from more than 0 second tosubstantially 20 seconds. More specifically, after the optical disc (M)is completely disposed in the optical disc apparatus 1, when the defocusvalue is changed stepwise within the predetermined range of numericvalues including the reference value 0 (FIGS. 8, 9, and 10) of thedefocus value being centered (FIG. 6A: S140, FIG. 6B: S141 to S146), toread each of the signals from the optical disc (M) (FIG. 1) and detecteach of the jitter values, so that the optimum defocus-value adjustmentof the OBL 4 for the optical disc (M) (FIG. 1) is performed based on thedifference value jitter(i_(a)d) between the maximum jitter valuejitter(i_(a)max) (FIGS. 8, 9, and 10) and the minimum jitter valuejitter(i_(a)min) of the detected jitter values (FIG. 6A: S160). Theabove defocus adjustment is preferably completed within a time periodfrom more than 0 second to substantially 15 seconds.

Since the time spent for the defocus-value adjusting method of theoptical disc apparatus 1 is set to a short time, there is swiftlycompleted the setting process when the defocus adjustment is performedin the optical disc apparatus 1 without waiting for a long time due tothe defocus adjustment. After the optical disc (M) is completelydisposed in the optical disc apparatus 1, when the defocus value ischanged stepwise within the predetermined range of numeric valuesincluding the reference value 0 of the defocus value being centered, toread each of the signals from the optical disc (M) and detect each ofthe jitter values so that the defocus adjustment of the OBL 4 for theoptical disc (M) is performed based on the difference valuejitter(i_(a)d) between the maximum jitter value jitter(i_(a)max) and theminimum jitter value jitter(i_(a)min) of the detected jitter values, thedefocus adjustment is performed within a time period from more than 0second to substantially 20 seconds, preferably, within a time periodfrom more than 0 second to substantially 15 seconds. Therefore, asituation is avoided where one must wait for a very long time due to thedefocus adjustment automatically performed by the optical disc apparatus1 from the time when the optical disc (M) is disposed in the opticaldisc apparatus 1 to the time when the main data/information/signals ofthe optical disc (M) are started to be read.

FIG. 8 is a characteristic view of a relationship between the jittervalue and the defocus value when it is determined in the CPU 10 (FIG. 1)that (jitter(i_(a)max)−jitter(i_(a)min)>jitter(i_(a)s) is satisfied(FIG. 6A, S160: YES).

When performing the defocus adjustment of the OBL 4 for the optical disc(M) (FIG. 1), if it is determined that the difference valuejitter(i_(a)d) between the maximum jitter value jitter(i_(a)max) and theminimum jitter value jitter(i_(a)min) is a value greater than thepredetermined value jitter(i_(a)s) as shown in FIG. 8, the defocus valuecorresponding to the minimum jitter value jitter(i_(a)min) is set as theoptimum defocus value.

The minimum jitter value jitter(i_(a)min) is smaller than the jittervalue jitter(i_(a)f) that is smaller than the maximum jitter valuejitter(i_(a)max) by the determination value jitter(i_(a)s), for example.In such a case, in the optical disc apparatus 1, there is performed theoperation of setting the defocus value corresponding to the minimumjitter value jitter(i_(a)min), i.e., the defocus value greater than thereference value 0 by +6% as the optimum defocus value for the focusingservo circuit 31.

In the program in the CPU 10 (FIG. 1), the next setting is performedbased on the value of [jitter(i_(a)max)−jitter(i_(a)min)]. If the valueof [jitter(i_(a)max)−jitter(i_(a)min)] exceeds a certain valuejitter(i_(a)s), “DEFOCUS” is set to “2%×i_(a)min”, for example. Thedefocus adjustment is completed in this way.

When the defocus-value setting operation is performed as above, thedefocus value greater than the reference defocus value 0 by +6% is setfor the focusing servo circuit 31, and the focusing servo operation ofthe focusing servo circuit 31 is performed centering the set defocusvalue.

By performing the defocus-value adjusting method of the optical discapparatus 1 as above, the OPU 2 making up the optical disc apparatus 1performs the stable focusing servo operation for the optical disc (M).The optical disc (M): when it is determined that the difference valuejitter(i_(a)d) between the maximum jitter value jitter(i_(a)max)therefor and the minimum jitter value jitter(i_(a)min) therefor is avalue greater than the predetermined value jitter(i_(a)s); is consideredas the optical disc (M) with poor jitter characteristics. Since thedefocus value corresponding to the minimum jitter value jitter(i_(a)min)is set as the optimum defocus value when reading a signal from theoptical disc (M) with the poor jitter characteristics, the stablefocusing servo operation is performed in the OPU 2.

If it is determined that[jitter(i_(a)max)−jitter(i_(a)min)>jitter(i_(a)s)] is not satisfied atthe step of S160 shown in FIG. 6A (S160: NO), the reference defocusvalue 0 is set as the optimum defocus value (S180).

FIG. 9 is a characteristic view of a relationship between the jittervalue and the defocus value when it is determined in the CPU 10 (FIG. 1)that [jitter(i_(a)max)−jitter(i_(a)min)>jitter(i_(a)s)] is not satisfied(FIG. 6A, S160: NO).

When performing the defocus adjustment of the OBL 4 for the optical disc(M) (FIG. 1), if it is determined that the difference valuejitter(i_(a)d) between the maximum jitter value jitter(i_(a)max) and theminimum jitter value jitter(i_(a)min) is a small value equal to orsmaller than the predetermined value jitter(i_(a)s) as shown in FIG. 9,the reference value 0 of the defocus value is set as the optimum defocusvalue. If the value of maximum value−minimum value (MAX−MIN) of thejitter values is equal to or smaller than a certain value, the defocusvalue is set to ±0. For example, when the jitter values with a waveshape shown in FIG. 9 are detected, if it is determined that the jittervalue jitter(i_(a)o) at the reference value 0 of the defocus value is avalue greater than the predetermined jitter value jitter(i_(a)f) andthat the difference value jitter(i_(a)d) between the maximum jittervalue jitter(i_(a)max) and the minimum jitter value jitter(i_(a)min) isa small value equal to or smaller than the predetermined valuejitter(i_(a)s), the defocus value is set to ±0. Alternatively, forexample, when the jitter values with a wave shape shown in FIG. 9 aredetected, if it is determined that all the jitter values are valuesgreater than the predetermined jitter value jitter(i_(a)f) and that thedifference value jitter(i_(a)d) between the maximum jitter value jitter(i_(a)max) and the minimum jitter value jitter(i_(a)min) is a smallvalue equal to or smaller than the predetermined value jitter(i_(a)s),the defocus value is set to ±0.

The minimum jitter value jitter(i_(a)min) is greater than the jittervalue jitter(i_(a)f) that is smaller than the maximum jitter valuejitter(i_(a)max) by the determination value jitter(i_(a)s), for example.In such a case, since the changes in the jitter values are small, thereis performed the operation of setting the reference defocus value as theoptimum defocus value for the focusing servo circuit 31 in the opticaldisc apparatus 1.

In the program in the CPU 10 (FIG. 1), the next setting is performedbased on the value of [jitter(i_(a)max)−jitter(i_(a)min)]. If the valueof [jitter(i_(a)max)−jitter(i_(a)min)] is equal to or smaller than acertain value jitter(i_(a)s), “DEFOCUS” is set to 0. The defocusadjustment is completed in this way.

When the defocus-value setting operation is performed as above, thefocusing servo operation of the focusing servo circuit 31 is performedwith the reference defocus value 0 being centered. Since the focusingservo operation is performed with the reference defocus value 0 beingcentered, the focusing control can stably be performed in the OPU 2.

By performing the defocus-value adjusting method of the optical discapparatus 1 as above, the OPU 2 making up the optical disc apparatus 1performs the stable focusing servo operation for the optical disc M. Theoptical disc M: when it is determined that the difference valuejitter(i_(a)d) between the maximum jitter value jitter(i_(a)max)therefor and the minimum jitter value jitter(i_(a)min) therefor is asmall value equal to or smaller than the predetermined valuejitter(i_(a)s); is considered as the optical disc M with relatively goodjitter characteristics. Since the reference value 0 of the defocus valueis set as the optimum defocus value in the optical disc apparatus 1 whenreading a signal from the optical disc M with the relatively good jittercharacteristics, the stable focusing servo operation is performed in theOPU 2 without malfunction occurring in the focusing servo operation ofthe OPU 2. The setting of the defocus value can easily be performed inthe optical disc apparatus 1.

When performing the defocus adjustment of the OBL 4 for the optical disc(M) (FIG. 1), if it is determined that the difference valuejitter(i_(a)d) between the maximum jitter value jitter(i_(a)max) and theminimum jitter value jitter(i_(a)min) is a small value equal to orsmaller than the predetermined value jitter(i_(a)s) as shown in FIG. 10,the reference value 0 of the defocus value is set as the optimum defocusvalue. If the value of maximum value−minimum value (MAX−MIN) of thejitter values is equal to or smaller than a certain value, the defocusvalue is set to ±0. For example, when the jitter values with a waveshape shown in FIG. 10 are detected, if it is determined that the jittervalue jitter(i_(a)o) at the reference value 0 of the defocus value is avalue greater than the predetermined jitter value jitter(i_(a)f) andthat the difference value jitter(i_(a)d) between the maximum jittervalue jitter(i_(a)max) and the minimum jitter value jitter(i_(a)min) isa small value equal to or smaller than the predetermined valuejitter(i_(a)s), the defocus value is set to ±0. In such a case, sincethe changes in the jitter values are small, there is performed theoperation of setting the reference defocus value as the optimum defocusvalue for the focusing servo circuit 31 in the optical disc apparatus 1.

In the program in the CPU 10 (FIG. 1) the next setting is performedbased on the value of [jitter(i_(a)max)−jitter(i_(a)min)] If the valueof [jitter(i_(a)max)−jitter(i_(a)min)] is equal to or smaller than acertain value jitter(i_(a)s), “DEFOCUS” is set to 0. The defocusadjustment is completed in this way.

When the defocus-value setting operation is performed as above, thefocusing servo operation of the focusing servo circuit 31 is performedcentering the reference defocus value 0. Since the focusing servooperation is performed centering the reference defocus value 0, thefocusing control can stably be performed in the OPU 2.

By performing the defocus-value adjusting method of the optical discapparatus 1 as above, the OPU 2 making up the optical disc apparatus 1performs the stable focusing servo operation for the optical disc M. Theoptical disc M: when it is determined that the difference value jitter(i_(a)d) between the maximum jitter value jitter(i_(a)max) therefor andthe minimum jitter value jitter(i_(a)min) therefor is a small valueequal to or smaller than the predetermined value jitter(i_(a)s); isconsidered as the optical disc M with relatively good jittercharacteristics. Since the reference value 0 of the defocus value is setas the optimum defocus value in the optical disc apparatus 1 whenreading a signal from the optical disc M with the relatively good jittercharacteristics, the stable focusing servo operation is performed in theOPU 2 without malfunction occurring in the focusing servo operation ofthe OPU 2. The setting of the defocus value can easily be performed inthe optical disc apparatus 1.

After the optical disc (M) is completely disposed in the optical discapparatus 1, each of the signals is read from the optical disc (M) andeach of the jitter values is detected, to perform the defocus adjustmentof the OBL 4 for the optical disc (M). The defocus adjustment isperformed within a time period from more than 0 second to substantially15 seconds. More specifically, after the optical disc (M) is completelydisposed in the optical disc apparatus 1, when the defocus value ischanged stepwise within the predetermined range of numeric valuesincluding the reference value 0 (FIGS. 8, 9, and 10) of the defocusvalue being centered (FIG. 6A: S140, FIG. 6B: S141 to S146), to read thesignal from the optical disc (M) (FIG. 1) and detect the jitter values,so that the optimum defocus-value adjustment of the OBL 4 for theoptical disc (M) (FIG. 1) is performed based on the difference valuejitter(i_(a)d) between the maximum jitter value jitter(i_(a)max) (FIGS.8, 9, and 10) and the minimum jitter value jitter(i_(a)min) of thedetected jitter values (FIG. 6A: S160). The above defocus adjustment ispreferably completed within a time period from more than 0 second tosubstantially 10 seconds.

Since the time spent for the defocus-value adjusting method of theoptical disc apparatus 1 is set to a short time, there is swiftlycompleted the setting process when the defocus adjustment is performedin the optical disc apparatus 1 without waiting for a long time due tothe defocus adjustment. After the optical disc (M) is completelydisposed in the optical disc apparatus 1, when the defocus value ischanged stepwise within the predetermined range of numeric valuesincluding the reference value 0 of the defocus value being centered, toread the signal from the optical disc (M) and detect the jitter values,so that the defocus adjustment of the OBL 4 for the optical disc (M) isperformed based on the difference value jitter(i_(a)d) between themaximum jitter value jitter(i_(a)max) and the minimum jitter valuejitter(i_(a)min) of the detected jitter values; since the defocusadjustment is performed within a time period from more than 0 second tosubstantially 15 seconds, preferably, within a time period from morethan 0 second to substantially 10 seconds; a situation is avoided whereone must wait for a very long time due to the defocus adjustmentautomatically performed by the optical disc apparatus 1 from the timewhen the optical disc (M) is disposed in the optical disc apparatus 1 tothe time when the main data/information/signals of the optical disc (M)are started to be read.

As described above, when the defocus adjustment of the OBL 4 isperformed for the optical disc (M) (FIG. 1) and the optimum defocusvalue is set in the optical disc apparatus 1, the jitter value is firstdetected based on the reference value 0 (FIGS. 8, 9, and 10) of thedefocus value, and if it is determined that the detected jitter valuejitter(i_(a)o) based on the reference value 0 of the defocus value is avalue greater than the predetermined jitter value jitter(i_(a)f), thereis then executed a jitter-value detecting process of detecting each ofthe jitter values every time the defocus value is changed stepwisewithin the predetermined range (e.g., −8% to +8%/−10% to +10%) ofnumeric values including the reference value 0 of the defocus value.

The optimum defocus value is set in the optical disc apparatus 1 byperforming the defocus-value adjusting method of the optical discapparatus 1 (FIG. 1) as above. When the defocus adjustment of the OBL 4is performed for the optical disc (M) and the optimum defocus value isset in the optical disc apparatus 1, the jitter value jitter(i_(a)o)based on the reference value 0 of the defocus value is first detected(FIG. 6A: S120). As shown in FIGS. 8, 9, and 10, the optical disc (M)(FIG. 1): if it is determined that the jitter value jitter(i_(a)o)therefor based on the reference value 0 of the defocus value is a valuegreater than the predetermined jitter value jitter(i_(a)f); isconsidered as the optical disc (M) in need of detecting/checking each ofthe jitter values corresponding to each of the defocus values. As shownin FIG. 6A, if it is determined that the detected jitter valuejitter(i_(a)o) based on the reference value 0 of the defocus value is avalue greater than the predetermined jitter value jitter(i_(a)f) (S130:YES), there are then performed the jitter-value detecting/comparing anddetermining/optimum value setting processes in which: each of the jittervalues is detected every time the defocus value is changed stepwisewithin the predetermined range (e.g., −8% to +8%/−10% to +10%) ofnumeric values including the reference value 0 of the defocus value(FIG. 6A: S140, FIG. 6B: S141 to S146); and the optimum defocus value isset based on the difference value jitter(i_(a)d) between the maximumjitter value jitter(i_(a)max) and the minimum jitter valuejitter(i_(a)min) of the detected jitter values (FIG. 6A: S140, FIG. 6B:S141 to S146, FIG. 6A: S150, S160, S170/S180).

When the defocus value is changed stepwise within the predeterminedrange (e.g., −10% to +10%/−8% to +8%) of numeric values including thereference value 0 (FIGS. 8, 9, and 10) of the defocus value, a dividedwidth of the defocus value is set to, for example, a value within arange from 0.5% to 5%, specifically, a value within a range from 1% to4% of the whole defocus values. If the divided width of the defocusvalue is a small divided width, for example, less than 0.5% of the wholedefocus values, since a large amount of data is to be acquired, it isfeared that the time spent for the defocus adjustment may be prolongedsince a large amount of data is to be acquired. If the divided width ofthe defocus value is a great divided width, for example, greater than 5%of all the defocus values, since the number of acquired data isinsufficient, it is feared that the accurate defocus adjustment may notbe performed. By setting the divided width of the defocus value to avalue within a range from 1% to 4% of the whole defocus values,preferably, by setting the divided width of the defocus value to 2% ofthe whole defocus values, the time spent for the defocus adjustment isnot so prolonged and the relatively accurate defocus adjustment isperformed.

As shown in FIGS. 11 and 12, before there is performed the operation fordetecting the jitter value every time the defocus value is changedstepwise within the predetermined range of numeric values including thereference value 0 of the defocus value being centered, the jitter valueis detected based on the reference value 0 of the defocus value, and ifit is determined that the detected jitter value jitter(i_(a)o) based onthe reference value 0 of the defocus value is a small value equal to orsmaller than the predetermined jitter value jitter(i_(a)f), thereference value 0 of the defocus value is set as the optimum defocusvalue.

Specifically, when the defocus adjustment of the OBL 4 is performed forthe optical disc (M) (FIG. 1) and the optimum defocus value is set inthe optical disc apparatus 1, the jitter value is first detected basedon the reference value 0 (FIG. 11) of the defocus value: and if it isdetermined that the detected jitter value jitter(i_(a)o) based on thereference value 0 of the defocus value is a small value equal to orsmaller than the predetermined jitter value jitter(i_(a)f), thejitter-value detecting process is omitted without detecting each of thejitter values every time the defocus value is changed stepwise withinthe predetermined range of numeric values including the reference value0 of the defocus value; and the reference value 0 of the defocus valueis set as the optimum defocus value immediately after the detectingprocess of the jitter value jitter(i_(a)o) based on the reference value0 of the defocus value and the comparing and determining process betweenthe predetermined jitter value jitter(i_(a)f) and the jitter valuejitter(i_(a)o) based on the reference value 0 of the defocus value.

When the defocus value is ±0, if the jitter value jitter(i_(a)o) is asmall value equal to or smaller than the predetermined jitter valuejitter(i_(a)f), the optimum defocus value is set to ±0. If the opticaldisc M with good jitter characteristics is used, the stability of thefocusing servo is prioritized.

By performing the defocus-value adjusting method of the optical discapparatus 1 (FIG. 1) as above, when the optical disc M with good jittercharacteristics is used, the defocus value is swiftly set and the OPU 2making up the optical disc apparatus 1 performs the stable focusingservo operation for the optical disc M. When the defocus adjustment ofthe OBL 4 is performed for the optical disc M and the optimum defocusvalue is set in the optical disc apparatus 1, the jitter valuejitter(i_(a)o) based on the reference value 0 of the defocus value isfirst detected (FIG. 6A: S120). As shown in FIG. 11, the optical disc M(FIG. 1): if it is determined that the jitter value jitter(i_(a)o)therefor based on the reference value 0 of the defocus value is a smallvalue equal to or smaller than the predetermined jitter valuejitter(i_(a)f); is considered as the optical disc M with good jittercharacteristics.

When reading the signal from the optical disc M with good jittercharacteristics: the jitter-value detecting/comparing and determiningprocesses (FIG. 6A: S140, FIG. 6B: S141 to S146, FIG. 6A: S150, S160)are omitted without detecting each of the jitter values every time thedefocus value is changed stepwise within the predetermined range ofnumeric values including the reference value 0 of the defocus value; andthe reference value 0 of the defocus value is set as the optimum defocusvalue in the optical disc apparatus 1 (FIG. 6A: S180) immediately afterthe detecting process (FIG. 6A: S120) of the jitter value jitter(i_(a)o)based on the reference value 0 of the defocus value and the comparingand determining process (FIG. 6A: S130) between the predetermined jittervalue jitter(i_(a)f) and the jitter value jitter(i_(a)o) based on thereference value 0 of the defocus value. Therefore, the setting time ofthe defocus value is reduced in the optical disc apparatus 1. Whenreading the signal from the optical disc M with good jittercharacteristics, since the reference value 0 of the defocus value is setas the optimum defocus value in the optical disc apparatus 1, the stablefocusing servo operation is performed in the OPU 2 without malfunctionoccurring in the focusing servo operation of the OPU 2.

When the defocus adjustment of the OBL 4 is performed for the opticaldisc M (FIG. 1) and the optimum defocus value is set in the optical discapparatus 1, the jitter value is first detected based on the referencevalue 0 (FIG. 12) of the defocus value: and if it is determined that thedetected jitter value jitter(i_(a)o) based on the reference value 0 ofthe defocus value is a small value equal to or smaller than thepredetermined jitter value jitter(i_(a)f), the jitter-value detectingprocess is omitted without detecting each of the jitter values everytime the defocus value is changed stepwise within the predeterminedrange of numeric values including the reference value 0 of the defocusvalue; and the reference value 0 of the defocus value is set as theoptimum defocus value immediately after the detecting process of thejitter value jitter(i_(a)o) based on the reference value 0 of thedefocus value and the comparing and determining process between thepredetermined jitter value jitter(i_(a)f) and the jitter valuejitter(i_(a)o) based on the reference value 0 of the defocus value.

When the defocus value is ±0, if the jitter value jitter(i_(a)o) is asmall value equal to or smaller than the predetermined jitter valuejitter(i_(a)f), the optimum defocus value is set to ±0. If the opticaldisc M with good jitter characteristics is used, the stability of thefocusing servo is prioritized.

By performing the defocus-value adjusting method of the optical discapparatus 1 (FIG. 1) as above, when the optical disc M with good jittercharacteristics is used, the defocus value is swiftly set and the OPU 2making up the optical disc apparatus 1 performs the stable focusingservo operation for the optical disc M. When the defocus adjustment ofthe OBL 4 is performed for the optical disc M and the optimum defocusvalue is set in the optical disc apparatus 1, the jitter valuejitter(i_(a)o) based on the reference value 0 of the defocus value isfirst detected (FIG. 6A: S120). As shown in FIG. 12, the optical disc M(FIG. 1): if it is determined that the jitter value jitter(i_(a)o)therefor based on the reference value 0 of the defocus value is a smallvalue equal to or smaller than the predetermined jitter valuejitter(i_(a)f); is considered as the optical disc M with good jittercharacteristics. Alternatively, for example, as shown in FIG. 12, theoptical disc M (FIG. 1): if it is determined that all the jitter valuesbetween the maximum jitter value jitter(i_(a)max) therefor and theminimum jitter value jitter(i_(a)min) therefor are small values equal toor smaller than the predetermined jitter value jitter (i_(a)f); isconsidered as the optical disc M with good jitter characteristics.

When the reading a signal from the optical disc M with good jittercharacteristics: the jitter-value detecting/comparing and determiningprocesses (FIG. 6A: S140, FIG. 6B: S141 to S146, FIG. 6A: S150, S160)are omitted without detecting each of the jitter values every time thedefocus value is changed stepwise within the predetermined range ofnumeric values including the reference value 0 of the defocus value; andthe reference value 0 of the defocus value is set as the optimum defocusvalue in the optical disc apparatus 1 (FIG. 6A: S180) immediately afterthe detecting process (FIG. 6A: S120) of the jitter value jitter(i_(a)o)based on the reference value 0 of the defocus value and the comparingand determining process (FIG. 6A: S130) between the predetermined jittervalue jitter(i_(a)f) and the jitter value jitter(i_(a)o) based on thereference value 0 of the defocus value. Therefore, the setting time ofthe defocus value is reduced in the optical disc apparatus 1. Whenreading the signal from the optical disc M with good jittercharacteristics, since the reference value 0 of the defocus value is setas the optimum defocus value in the optical disc apparatus 1, the stablefocusing servo operation is performed in the OPU 2 without malfunctionoccurring in the focusing servo operation of the OPU 2.

Since the defocus value ±0 is first measured and set, the measurementtime for detecting the jitter value can be reduced. It is possible toallow the optical disc apparatus 1 including the OPU 2 to perform thedefocus adjustment only for the optical disc (M) for which the jittervalue is presumed/determined as not good and the detection/check of eachof the jitter values is required. Since the defocus adjustment isperformed only for the optical disc (M) for which the jitter value ispresumed/determined that not good and the detection/check of each of thejitter values is required, the initial measurement time of the opticaldisc M with good jitter characteristics can be reduced in the OPU 2.Since the defocus value is set to ±0 for the optical disc M with goodjitter, the stable focusing servo can be performed for the optical discM with good jitter. Since the defocus value is set to ±0 for thefocusing servo circuit 31 when the optical disc apparatus 1 is disposedwith the optical disc M for which the jitter value therefore is notsubstantially changed, no focus drop, so-called F-drop, occurs and thestable focusing servo can be performed.

The focus drop means that the focus Ls (FIGS. 1, 2, and 4) of the laserbeam L emitted from the LD3 of the OPU 2 (FIG. 1) and having passedthrough the OBL 4 deviates from the pits Mt of an optical disc (M) in astate of being tracked, so that data recorded in the optical disc (M)becomes unable to be read.

As described above, in the defocus-value adjusting method of the opticaldisc apparatus 1, the jitter value is detected every time the defocusvalue is changed by the predetermined % within the predetermined rangecentering the reference value 0 of the defocus value, to perform theoperation of setting the optimum defocus value. Before such an operationis performed, the operation of detecting the jitter value is performedin the state where the defocus value is set to the reference defocusvalue defined as zero. If it is determined that the detected jittervalue jitter(i_(a)o) is a small value equal to or smaller than thepredetermined value jitter(i_(a)f), i.e., if it is determined that theoptical disc M has good reproduction characteristics, there is performedthe operation of setting the reference defocus value 0, as it is, as theoptimum defocus value in the optical disc apparatus 1.

If the jitter value jitter(i_(a)o) to be detected/set for thedetermining operation is detected as a small jitter value equal to orsmaller than, for example, a predetermined jitter value jitter(i_(a)f),the optical disc M is determined as a good disc, and the reproductionoperation can be performed without trouble even if the selectingoperation of the defocus value is not performed.

After the optical disc M with good jitter characteristics is completelydisposed in the optical disc apparatus 1, when performing the defocusadjustment of the OBL 4 for the optical disc M with good jittercharacteristics in the optical disc apparatus 1, the defocus adjustmentis performed within a time period from more than 0 second tosubstantially 3 seconds, preferably, a time period from more than 0second to substantially 1 second.

After the optical disc M with good jitter characteristics is completelydisposed in the optical disc apparatus 1, when performing the defocusadjustment of the OBL 4 for the optical disc M, the defocus adjustmentis performed within a time period from more than 0 second tosubstantially 3 seconds, preferably, a time period from more than 0second to substantially 1 second. Therefore, a situation is avoidedwhere one must wait for a long time due to the defocus adjustmentautomatically performed by the optical disc apparatus 1 from the timewhen the optical disc M is disposed in the optical disc apparatus 1 tothe time when the main data/information/signals of the optical disc Mare started to be read. When the optical disc M with good jittercharacteristics is disposed in the optical disc apparatus 1, the defocusadjustment in the optical disc apparatus 1 is swiftly completed in ashort time.

Description will then be made of a state when the track jump of the OPU2 is performed if the defocus value other than the reference value 0 isset.

First, the defocus adjustment of the optical disc apparatus 1 (FIG. 1)is performed. The defocus value is set to a numeric value other than thereference value 0 in this case. Before starting the track jump, thedefocus value is set to the reference value 0. The track jump operationis performed. After the track jump is completed, the defocus value isset back to the original numeric value other than the reference value 0.

Specifically describing the operation of the optical disc apparatus 1from the start to the end of the track jump process, if the optimumdefocus value is set to any one of biased numeric values other than thereference value 0 among the defocus values within the predeterminedrange (FIG. 6A: S170, FIG. 7, S191: NO, FIG. 8), when the OPU 2 isdriven to perform the track jump on the optical disc (M) (FIG. 1), thedefocus value is temporarily set to the reference value 0. After thedefocus value is temporarily set to the reference value 0 (FIG. 7:S192), the OPU 2 (FIG. 1) is driven to perform the track jump (FIG. 7:S193).

By setting the defocus value in the optical disc apparatus 1 (FIG. 1) asshown in the steps of S191 and S192 of FIG. 7, even if the optimumdefocus value is set to any one of biased numeric values (e.g., +6%)other than the reference value 0 of the defocus value among the defocusvalues within the predetermined range, the track jump of the OPU 2 onthe optical disc (M) is favorably performed. When the defocus adjustmentof the OPU 2 is performed for the optical disc (M), if the optimumdefocus value is set to a biased numeric value (+6%) other than thereference value 0, a track of the optical disc (M) may not be caughtwhen the track jump is performed by the OPU 2 on the optical disc (M).However, since the defocus value is temporarily set to the referencevalue 0 when the track jump is performed by the OPU 2, even if thedefocus value is set to a biased numeric value other than the referencevalue 0, the track jump becomes easily performed by the OPU 2 on theoptical disc (M) in a normal manner.

After the track jump of the OPU 2 is performed on the optical disc (M)(FIG. 1) (FIG. 7: S193) and the track jump operation is completed, thedefocus value is returned to the original biased numeric value (e.g.,+6%) other than the reference value 0 (FIG. 7: S195, FIG. 8). Since theoptimum defocus value of the initial setting was set to the biasednumeric value other than the reference value 0 (FIG. 7, S194: NO, FIG.8), the defocus value is returned to the original biased numeric value(e.g., +6%) other than the reference value 0 after the track jump iscompleted (FIG. 7: S195).

Therefore, the optimum defocus value is again set in the optical discapparatus 1. When the track jump of the OPU 2 is not performed on theoptical disc (M), a biased numeric value other than the reference value0 of the defocus value is again set as the optimum defocus value in theoptical disc apparatus 1 and, therefore, the focusing adjustment of theOBL 2 of the OPU 2 is favorably performed for the optical disc (M).Since the defocus value other than the reference value 0 stored earlierin the second memory circuit 12 is again set as the optimum defocusvalue in the optical disc apparatus 1, the optimum defocus value isswiftly set again.

Description will then be made of a state when the track jump of the OPU2 is performed if the optimum defocus value is set to the referencevalue 0. Specifically describing the operation of the optical discapparatus 1 from the start to the end of the track jump process when theoptimum defocus value is set to the reference value 0, if the optimumdefocus value is set to the reference value 0 (FIG. 7, S191: YES, FIGS.9, 10, 11, and 12), the OPU 2 (FIG. 1) is driven to perform the trackjump without changing the defocus value (FIG. 7: S193). Since theoptimum defocus value continues to be set to the reference value 0, thetrack jump continues to be performed by the OPU 2 on the optical discM/(M) (FIG. 1) in a normal manner. Since the optimum defocus value ofthe initial setting was set to the reference value 0 (FIG. 7, S194: YES,FIGS. 9, 10, 11, and 12), the defocus value is not changed after thetrack jump is completed and the optimum defocus value is maintained atthe reference value 0.

The detrack-value adjusting method of the disc apparatus 1 will then bedescribed.

FIG. 13A is a flowchart of an embodiment of the detrack-value adjustingmethod of the disc apparatus; FIG. 13B is a flowchart of thejitter-value detecting process of the detrack-value adjusting method ofthe disc apparatus; FIG. 14 is a flowchart of a track jump process whenperforming the detrack-value adjusting method of the disc apparatus;FIG. 15 is a graphical representation of a relationship between thedetrack value and the jitter value; FIG. 16 is also a graphicalrepresentation of a relationship between the detrack value and thejitter value; FIG. 17 is also a graphical representation of arelationship between the detrack value and the jitter value; FIG. 18 isalso a graphical representation of a relationship between the detrackvalue and the jitter value; and FIG. 19 is also a graphicalrepresentation of a relationship between the detrack value and thejitter value.

The detrack-value adjusting method of the optical disc apparatus 1 willbe described with reference to the figures in conjunction withflowcharts shown in FIGS. 13A, 13B, and 14.

The detrack adjusting method of the optical disc apparatus 1 based onthe jitter value is performed as follows. The offset adjustment of thetrack is performed at the time of initial data reading or immediatelyafter the initial data reading of the OPU 2 in the vicinity of the discinner circumferential portion Mc immediately before performing the datareproduction of the reproduction/recording optical disc M (FIG. 1), forexample. At this time, there are performed the detrack-value adjustmentprocess, etc. corresponding to the reference voltage value (Vref), forexample. For example, in the optical disc apparatus 1, there is read asignal having the shape of S-curve substantially laid sideways with −50%to +50% of the detrack values centering a reference value 0, which isthe reference voltage value (Vref).

The optical disc apparatus 1 is used to perform the tracking adjustmentof the OBL 4 for the signal face portion Ms of the optical disc M. Theoptical disc apparatus 1 is used to perform the detrack-value adjustingmethod in the optical disc apparatus 1.

For example, when the optical disc apparatus 1 is turned on,preparations are started for performing the detrack-value adjustingmethod of the optical disc apparatus 1. When the optical disc apparatus1 is turned on and the optical disc apparatus 1 is rendered in thepower-on state, for example, data such as various pieces of informationare sent from the memory circuit 11 such as the ROM 11 to the systemcontrol circuit 10. At this point, various data, for example, apredetermined jitter value jitter(i_(b)f) and a determination valuejitter(i_(b)s) are sent to the system control circuit 10 and set in thesystem control circuit 10 (FIG. 13A: S210).

The detrack-value adjusting method of this optical disc apparatus 1(FIG. 1) is a detrack-value adjusting method of the optical discapparatus 1 that performs the tracking adjustment of the OBL 4 for theoptical disc M with the use of the optical disc apparatus 1 includingthe OPU 2 having the OBL 4 by detecting the jitter value of the signalread from the optical disc M and by adjusting the detrack value used formoving the OBL 4 in the radial direction Dt of the optical disc M whenthe OBL 4 of the OPU 2 is focused on the signal face portion Ms of theoptical disc M based on the detected jitter value. The detrack-valuesetting process is performed as follows.

By disposing the optical disc M in the optical disc apparatus 1, theoperation is substantially started for setting the suitable detrackvalue in the optical disc apparatus 1. First, track bias, so-calleddetrack is applied to the tracking coil (TRACKING COIL) 72 to measurethe jitter with the use of the optical disc apparatus 1. When causingthe optical disc apparatus 1 to perform the detrack-value adjustingmethod, the jitter is first detected/measured at the detrack value of ±0(FIG. 13A: S220). At this point, for example, as shown in FIG. 18 orFIG. 19, if it is determined that a jitter value jitter(i_(b)o) at thedetrack value of ±0 is a small value equal to or smaller than aspecified value jitter(i_(b)f) and the program in the CPU 10 determinesthat the optical disc M (FIG. 1) has good jitter characteristics (FIG.13A, S230: NO), the detrack value is set to zero (FIG. 13A: S280) andthe detrack adjustment is completed.

This optical disc apparatus 1 (FIG. 1) performs a differentdetrack-value adjusting method for each of the optical disc M with goodjitter characteristics and the optical disc (M) presumed/determined tohave the jitter characteristics that are not good and requiring thedetection/check of jitter values.

When the detrack-value adjusting method in the optical disc apparatus 1is performed with the use of the optical disc apparatus 1, for example,as shown in FIGS. 15, 16, and 17, jitter values are detected/measured asneeded. Specifically, in the case of the optical disc (M) for which: itis determined that the jitter value jitter (i_(b)o) at the detrack valueof ±0 is a value greater than the specified value jitter (i_(b)f); theprogram in the CPU 10 (FIG. 1) presumes/determines that the jittercharacteristics are not good; and it is also determined that each of thejitter values requires the detection/check, the following measurement isperformed. First, when reading the signal from the optical disc (M) todetect the jitter value, the detrack value within a predetermined rangeis changed. Specifically, when reading the signal from the optical disc(M) to detect the jitter value, the detrack value is changed stepwisewithin a predetermined range of numeric values including the referencevalue 0 of the detrack value (FIGS. 15, 16, and 17) being centered (FIG.13A: S240, FIG. 13B: S241 to S246). Every time the detrack value ischanged stepwise, the jitter value is detected.

The operation of setting the detrack value is performed by thedetrack-value setting circuit 22 in the state of performing thereproduction operation for the signal recorded in the optical disc (M)(FIG. 1). In the detrack-value setting circuit 22, a value of thedetrack value set for the tracking servo circuit 32 is changed in astepwise of 2% from −8% to +8% relative to the reference value 0 (FIGS.15, 16, and 17). At the same time, the jitter value of the reproductionsignal is detected correspondingly to the detrack values by the jittermeasurement circuit 9 to set the detrack value.

Specifically, while the detrack value for the tracking servo circuit 32is set by the detrack-value setting circuit 22 to a value lower than thereference value 0 by substantially −8%, the reproduction operation isperformed for the signal recorded in the optical disc (M) to detect thejitter value included in the reproduction signal with the jittermeasurement circuit 9. The jitter value detected in this way is storedin the memory circuit 12 such as the RAM 12 along with the detrackvalue.

As the detrack value is changed in a stepwise of 2% from −8% to +8%relative to the reference value 0, the jitter value corresponding to thedetrack value is detected and the jitter value is stored in the memorycircuit 12 along with the detrack value. The operations are repeatedlyperformed.

When the operation is started for setting the detrack value in theoptical disc apparatus 1, in the case of the optical disc (M) for whichit is determined that the jitter values require detection/check duringthe process of the detrack adjusting method of the optical discapparatus 1, the operation of detecting the jitter value is firstperformed every time the detrack value is changed within a predeterminedrange (FIG. 13A: S240, FIG. 13B: S241 to S246). The predetermined rangeis defined, for example, if the detrack value 0 is defined as areference value, as the detrack values from −10% to +10% to be set forthe tracking servo circuit 32 relative to the reference value (FIGS. 15,16, and 17). The preferable predetermined range of detrack values isdefined, for example, if the detrack value 0 is defined as a referencevalue, as a range from −8% to +8% to be set for the tracking servocircuit 32 relative to the reference value.

For example, if the detrack value is set to a value smaller than the−10% value, the tracking servo function may not work normally.Alternatively, for example, if the detrack value is set to a valuegreater than the +10% value, the tracking servo function may not worknormally. Therefore, the detrack values from −10% to +10% centering thereference value 0 of the detrack value may be set for the tracking servocircuit 32. Preferably, the tracking servo function works normally bysetting the detrack values from −8% to +8% centering the reference value0 of the detrack value for the tracking servo circuit 32.

For example, in the case of the optical disc (M) (FIG. 1) for which: itis determined that the jitter value jitter(i_(b)o) at the referencevalue 0 of the detrack value (FIGS. 15, 16, and 17) is a value greaterthan the specified value jitter(i_(b)f); it is presumed/determined thatthe jitter value is not good; and it is also determined that each of thejitter values requires detection/check, the following process isperformed under the control of the program in the CPU 10. The followingprocess is performed by the CPU 10 and the second memory circuit 12.

First, an initial value is set by the program in the CPU 10 to seti_(b)=−4 (FIG. 13B: S241). For example, a value of “DETRACK=2%×i_(b)” isset (SET) to “TRACK_BIAS” (S242). The jitter value is measured by theOPU 2 (S243) and the result is stored in the second memory circuit 12 as“jitter(i_(b))” (S244).

The “i_(b)” is incremented by the program in the CPU 10 (S241, S242 toS246).

In the case of “i_(b)<5” (S246: NO), a value of “DETRACK=2%×i_(b)” isset to “TRACK_BIAS” (S242) and the jitter is measured again by the OPU 2(S243) to store the result in the second memory circuit 12 as“jitter(i_(b))” (S244). In the case of “i_(b)≧5” (S246: YES), a minimumvalue is obtained from “jitter(i_(b))”, and “i_(b)” at this point isdefined as “i_(b)min” (FIG. 13A: S250). In the case of “i_(b)≧5” (FIG.13B, S246: YES), a maximum value is obtained from “jitter(i_(b))”, and“i_(b)” at this point is defined as “i_(b)max” (FIG. 13A: S250).

The optimum detrack value is then set based on a difference valuejitter(i_(b)d) between the maximum jitter value jitter(i_(b)max) and theminimum jitter value jitter(i_(b)min) of the detected jitter values(S260).

The detrack value is changed within the predetermined range: thedetection operation of each of the jitter values is performed (FIG. 13A:S240, FIG. 13B: S241 to S246); and the maximum jitter value jitter(i_(b)max) and the minimum jitter value jitter(i_(b)min) are selectedfrom the detected jitter values (FIG. 13A: S250).

After performing the selection setting operation at the step of S250 isperformed, there is performed a determination operation which determineswhether [jitter(i_(b)max)−jitter(i_(b)min)>jitter(i_(b)s)] is satisfied(S260: YES) or [jitter(i_(b)max)−jitter(i_(b)min)>jitter(i_(b)s)] is notsatisfied (S260: NO). If it is determined that[jitter(i_(b)max)−jitter(i_(b)min)>jitter(i_(b)s)] is satisfied at thestep of S260 (S260: YES), the detrack value corresponding to the minimumjitter value jitter(i_(b)min) is set as the optimum detrack value(S270). Alternatively, if it is determined that[jitter(i_(b)max)−jitter(i_(b)min)>jitter(i_(b)s)] is not satisfied atthe step of S260 (S260: NO), the reference value 0 of the detrack valueis set as the optimum detrack value (S280).

The optimum detrack value is set in the optical disc apparatus 1 byperforming the detrack-value adjusting method of the optical discapparatus 1 as above. The jitter value is detected as needed every timethe detrack value is changed stepwise within the predetermined range ofnumeric values including the reference value 0 of the detrack valuebeing centered, so that the optimum detrack value is set based on thedifference value jitter(i_(b)d) between the maximum jitter valuejitter(i_(b)max) and the minimum jitter value jitter(i_(b)min) of thedetected jitter values. Therefore, the optimum detrack value is set inthe optical disc apparatus 1. Since the optimum detrack value is set inthe optical disc apparatus 1, the OPU 2 performs the stable trackingservo operation for the optical disc M. The detrack value settingoperation can easily be performed in the optical disc apparatus 1.

After the optical disc (M) is completely disposed in the optical discapparatus 1, when reading each of the signals from the optical disc (M)and detecting each of the jitter values to perform the detrackadjustment of the OBL 4 for the optical disc (M), the detrack adjustmentis performed within a time period from more than 0 second tosubstantially 20 seconds. More specifically, after the optical disc (M)is completely disposed in the optical disc apparatus 1, when the detrackvalue is changed stepwise within the predetermined range of numericvalues including the reference value 0 (FIGS. 15, 16, and 17) of thedetrack value being centered (FIG. 13A: S240, FIG. 13B: S241 to S246),to read each of the signals from the optical disc (M) (FIG. 1) anddetect each of the jitter values, so that the optimum detrack-valueadjustment of the OBL 4 for the optical disc (M) (FIG. 1) is performedbased on the difference value jitter(i_(b)d) between the maximum jittervalue jitter(i_(b)max) (FIGS. 15, 16, and 17) and the minimum jittervalue jitter(i_(b)min) of the detected jitter values (FIG. 13A: S260).The above detrack adjustment is preferably completed within a timeperiod from more than 0 second to substantially 15 seconds.

Since the time spent for the detrack-value adjusting method of theoptical disc apparatus 1 is set to a short time, there is swiftlycompleted the setting process when the detrack adjustment is performedin the optical disc apparatus 1 without waiting for a long time due tothe detrack adjustment. After the optical disc (M) is completelydisposed in the optical disc apparatus 1, when the detrack value ischanged stepwise within the predetermined range of numeric valuesincluding the reference value 0 of the detrack value being centered, toread each of the signals from the optical disc (M) and detect each ofthe jitter values, so that the detrack adjustment of the OBL 4 for theoptical disc (M) is performed based on the difference valuejitter(i_(b)d) between the maximum jitter value jitter(i_(b)max) and theminimum jitter value jitter(i_(b)min) of the detected jitter values, thedetrack adjustment is performed within a time period from more than 0second to substantially 20 seconds, preferably, within a time periodfrom more than 0 second to substantially 15 seconds. Therefore, asituation is avoided where one must wait for a very long time due to thedetrack adjustment automatically performed by the optical disc apparatus1 from the time when the optical disc (M) is disposed in the opticaldisc apparatus 1 to the time when the main data/information/signals ofthe optical disc (M) are started to be read.

FIG. 15 is a characteristic view of a relationship between the jittervalue and the detrack value when it is determined in the CPU 10 (FIG. 1)that [jitter(i_(b)max)−jitter(i_(b)min)>jitter(i_(b)s)] is satisfied(FIG. 13A, S260: YES).

When performing the detrack adjustment of the OBL 4 for the optical disc(M) (FIG. 1), if it is determined that the difference valuejitter(i_(b)d) between the maximum jitter value jitter(i_(b)max) and theminimum jitter value jitter(i_(b)min) is a value greater than thepredetermined value jitter(i_(b)s) as shown in FIG. 15, the detrackvalue corresponding to the minimum jitter value jitter(i_(b)min) is setas the optimum detrack value.

The minimum jitter value jitter(i_(b)min) is smaller than the jittervalue jitter(i_(b)f) that is smaller than the maximum jitter valuejitter(i_(b)max) by the determination value jitter(i_(b)s), for example.In such a case, in the optical disc apparatus 1, there is performed theoperation of setting the detrack value corresponding to the minimumjitter value jitter(i_(b)min), i.e., the detrack value greater than thereference value 0 by +6% as the optimum detrack value for the trackingservo circuit 32.

In the program in the CPU 10 (FIG. 1), the next setting is performedbased on the value of [jitter(i_(b)max)−jitter(i_(b)min)]. If the valueof [jitter(i_(b)max)−jitter(i_(b)min)] exceeds a certain valuejitter(i_(b)s), “DETRACK” is set to “2%×i_(b)min”, for example. Thedetrack adjustment is completed in this way.

When the detrack-value setting operation is performed as above, thedetrack value greater than the reference detrack value 0 by +6% is setfor the tracking servo circuit 32, and the tracking servo operation ofthe tracking servo circuit 32 is performed centering the set detrackvalue.

By performing the detrack-value adjusting method of the optical discapparatus 1 as above, the OPU 2 making up the optical disc apparatus 1performs the stable tracking servo operation for the optical disc (M).The optical disc (M): when it is determined that the difference valuejitter(i_(b)d) between the maximum jitter value jitter(i_(b)max)therefor and the minimum jitter value jitter (i_(b)min) therefor is avalue greater than the predetermined value jitter (i_(b)s); isconsidered as the optical disc (M) with poor jitter characteristics.Since the detrack value corresponding to the minimum jitter valuejitter(i_(b)min) is set as the optimum detrack value when reading asignal from the optical disc (M) with the poor jitter characteristics,the stable tracking servo operation is performed in the OPU 2.

If it is determined that[jitter(i_(b)max)−jitter(i_(b)min)>jitter(i_(b)s)] is not satisfied atstep of S260 shown in FIG. 13A (S260: NO), the reference detrack value 0is set as the optimum detrack value (S280).

FIG. 16 is a characteristic view of a relationship between the jittervalue and the detrack value when it is determined in the CPU 10 (FIG. 1)that [jitter(i_(b)max)−jitter(i_(b)min)>jitter(i_(b)s)] is not satisfied(FIG. 13A, S260: NO).

When performing the detrack adjustment of the OBL 4 for the optical disc(M) (FIG. 1), if it is determined that the difference valuejitter(i_(b)d) between the maximum jitter value jitter(i_(b)max) and theminimum jitter value jitter(i_(b)min) is a small value equal to orsmaller than the predetermined value jitter(i_(b)s) as shown in FIG. 16,the reference value 0 of the detrack value is set as the optimum detrackvalue. If the maximum value−minimum value (MAX−MIN) of the jitter valuesis equal to or smaller than a certain value, the detrack value is set to±0. For example, when the jitter values with a wave shape shown in FIG.16 are detected, if it is determined that the jitter valuejitter(i_(b)o) at the reference value 0 of the detrack value is a valuegreater than the predetermined jitter value jitter(i_(b)f) and that thedifference value jitter(i_(b)d) between the maximum jitter valuejitter(i_(b)max) and the minimum jitter value jitter(i_(b)min) is asmall value equal to or smaller than the predetermined valuejitter(i_(b)s), the detrack value is set to ±0. Alternatively, forexample, when the jitter values with a wave shape shown in FIG. 16 aredetected, if it is determined that all the jitter values are valuesgreater than the predetermined jitter value jitter(i_(b)f) and that thedifference value jitter(i_(b)d) between the maximum jitter value jitter(i_(b)max) and the minimum jitter value jitter(i_(b)min) is a smallvalue equal to or smaller than the predetermined value jitter(i_(b)s),the detrack value is set to ±0.

The minimum jitter value jitter(i_(b)min) is greater than the jittervalue jitter(i_(b)f) that is smaller than the maximum jitter valuejitter(i_(b)max) by the determination value jitter(i_(b)s), for example.In such a case, since the changes in the jitter values are small, thereis performed the operation of setting the reference detrack value as theoptimum detrack value for the tracking servo circuit 32 in the opticaldisc apparatus 1.

In the program in the CPU 10 (FIG. 1), the next setting is performedbased on the value of [jitter(i_(b)max)−jitter(i_(b)min)]. If the valueof [jitter(i_(b)max)−jitter(i_(b)min)] is equal to or smaller than acertain value jitter(i_(b)s), “DETRACK” is set to 0. The detrackadjustment is completed in this way.

When the detrack-value setting operation is performed as above, thetracking servo operation of the tracking servo circuit 32 is performedcentering the reference detrack value 0. Since the tracking servooperation is performed centering the reference detrack value 0, thetracking control can stably be performed in the OPU 2.

By performing the detrack-value adjusting method of the optical discapparatus 1 as above, the OPU 2 making up the optical disc apparatus 1performs the stable tracking servo operation for the optical disc M. Theoptical disc M: when it is determined that the difference valuejitter(i_(b)d) between the maximum jitter value jitter(i_(b)max)therefor and the minimum jitter value jitter(i_(b)min) therefor is asmall value equal to or smaller than the predetermined valuejitter(i_(b)s); is considered as the optical disc M with relatively goodjitter characteristics. Since the reference value 0 of the detrack valueis set as the optimum detrack value in the optical disc apparatus 1 whenreading a signal from the optical disc M with the relatively good jittercharacteristics, the stable tracking servo operation is performed in theOPU 2 without malfunction occurring in the tracking servo operation ofthe OPU 2. The setting of the detrack value can easily be performed inthe optical disc apparatus 1.

When performing the detrack adjustment of the OBL 4 for the optical disc(M) (FIG. 1), if it is determined that the difference value jitter(i_(b)d) between the maximum jitter value jitter(i_(b)max) and theminimum jitter value jitter(i_(b)min) is a small value equal to orsmaller than the predetermined value jitter(i_(b)s) as shown in FIG. 17,the reference value 0 of the detrack value is set as the optimum detrackvalue. If the value of maximum value−minimum value (MAX−MIN) of thejitter values is equal to or smaller than a certain value, the detrackvalue is set to ±0. For example, when the jitter values with a waveshape shown in FIG. 17 are detected, if it is determined that the jittervalue jitter(i_(b)o) at the reference value 0 of the detrack value is avalue greater than the predetermined jitter value jitter(i_(b)f) andthat the difference value jitter(i_(b)d) between the maximum jittervalue jitter(i_(b)max) and the minimum jitter value jitter(i_(b)min) isa small value equal to or smaller than the predetermined valuejitter(i_(b)s), the detrack value is set to ±0. In such a case, sincethe changes in the jitter values are small, the optical disc apparatus 1performs the operation of setting the reference detrack value as theoptimum detrack value for the tracking servo circuit 32.

In the program in the CPU 10 (FIG. 1), the next setting is performedbased on the value of [jitter(i_(b)max)−jitter(i_(b)min)] If the valueof [jitter(i_(b)max)−jitter(i_(b)min)] is equal to or smaller than acertain value jitter(i_(b)s), “DETRACK” is set to 0. The detrackadjustment is completed in this way.

When the detrack-value setting operation is performed as above, thetracking servo operation of the tracking servo circuit 32 is performedwith the reference detrack value 0 being centered. Since the trackingservo operation is performed with the reference detrack value 0 beingcentered, the tracking control can stably be performed in the OPU 2.

By performing the detrack-value adjusting method of the optical discapparatus 1 as above, the OPU 2 making up the optical disc apparatus 1performs the stable tracking servo operation for the optical disc M. Theoptical disc M: when it is determined that the difference valuejitter(i_(b)d) between the maximum jitter value jitter(i_(b)max)therefor and the minimum jitter value jitter(i_(b)min) therefor is asmall value equal to or smaller than the predetermined valuejitter(i_(b)s); is considered as the optical disc M with relatively goodjitter characteristics. Since the reference value 0 of the detrack valueis set as the optimum detrack value in the optical disc apparatus 1 whenreading a signal from the optical disc M with the relatively good jittercharacteristics, the stable tracking servo operation is performed in theOPU 2 without malfunction occurring in the tracking servo operation ofthe OPU 2. The setting of the detrack value can easily be performed inthe optical disc apparatus 1.

After the optical disc (M) is completely disposed in the optical discapparatus 1, each of the signals is read from the optical disc (M) andeach of the jitter values is detected, to perform the detrack adjustmentof the OBL 4 for the optical disc (M). The detrack adjustment isperformed within a time period from more than 0 second to substantially15 seconds. More specifically, after the optical disc (M) is completelydisposed in the optical disc apparatus 1, when the detrack value ischanged stepwise within the predetermined range of numeric valuesincluding the reference value 0 (FIGS. 15, 16, and 17) of the detrackvalue being centered (FIG. 13A: S240, FIG. 13B: S241 to S246), to readthe signal from the optical disc (M) (FIG. 1) and detect the jittervalues, so that the optimum detrack-value adjustment of the OBL 4 forthe optical disc (M) (FIG. 1) is performed based on the difference valuejitter(i_(b)d) between the maximum jitter value jitter(i_(b)max) (FIGS.15, 16, and 17) and the minimum jitter value jitter(i_(b)min) of thedetected jitter values (FIG. 13A: S260). The above detrack adjustment ispreferably completed within a time period from more than 0 second tosubstantially 10 seconds.

Since the time spent for the detrack-value adjusting method of theoptical disc apparatus 1 is set to a short time as above, There isswiftly completed the setting process when the detrack adjustment isperformed in the optical disc apparatus 1 without waiting for a longtime due to the detrack adjustment. After the optical disc (M) iscompletely disposed in the optical disc apparatus 1, when the detrackvalue is changed stepwise within the predetermined range of numericvalues including the reference value 0 of the detrack value beingcentered, to read the signal from the optical disc (M) and detect thejitter values so that the detrack adjustment of the OBL 4 for theoptical disc (M) is performed based on the difference valuejitter(i_(b)d) between the maximum jitter value jitter(i_(b)max) and theminimum jitter value jitter(i_(b)min) of the detected jitter values;since the detrack adjustment is performed within a time period from morethan 0 second to substantially 15 seconds, preferably, within a timeperiod from more than 0 seconds to substantially 10 seconds, a situationis avoided where one must wait for a very long time due to the detrackadjustment automatically performed by the optical disc apparatus 1 fromthe time when the optical disc (M) is disposed in the optical discapparatus 1 to the time when the main data/information/signals of theoptical disc (M) are started to be read.

As described above, when the detrack adjustment of the OBL 4 isperformed for the optical disc (M) (FIG. 1) and the optimum detrackvalue is set in the optical disc apparatus 1, the jitter value is firstdetected based on the reference value 0 (FIGS. 15, 16, and 17) of thedetrack value, and if it is determined that the detected jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value is avalue greater than the predefined jitter value jitter(i_(b)f), ajitter-value detecting process is then executed to detect the jittervalue every time the detrack value is changed stepwise within thepredetermined range (e.g., −8% to +8%/−10% to +10%) of numeric valuesincluding the reference value 0 of the detrack value.

The optimum detrack value is set in the optical disc apparatus 1 byperforming the detrack-value adjusting method of the optical discapparatus 1 (FIG. 1) as above. When the detrack adjustment of the OBL 4is performed for the optical disc (M) and the optimum detrack value isset in the optical disc apparatus 1, the jitter value jitter(i_(b)o)based on the reference value 0 of the detrack value is first detected(FIG. 13A: S220). As shown in FIGS. 15, 16, and 17, the optical disc (M)(FIG. 1): if it is determined that the jitter value jitter(i_(b)o)therefor based on the reference value 0 of the detrack value is a valuegreater than the predetermined jitter value jitter(i_(b)f); isconsidered as the optical disc (M) in need of detecting/checking each ofthe jitter values corresponding to each of the detrack values. As shownin FIG. 13A, if it is determined that the detected jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value is avalue greater than the predetermined jitter value jitter(i_(b)f) (S230:YES), there are then performed the jitter-value detecting/comparing anddetermining/optimum value setting processes in which: each of the jittervalues is detected every time the detrack value is changed stepwisewithin the predetermined range (e.g., −8% to +8%/−10% to +10%) ofnumeric values including the reference value 0 of the detrack value(FIG. 13A: S240, FIG. 13B: S241 to S246); and the optimum detrack valueis set based on the difference value jitter(i_(b)d) between the maximumjitter value jitter(i_(b)max) and the minimum jitter valuejitter(i_(b)min) of the detected jitter values (FIG. 13A: S240, FIG.13B: S241 to S246, FIG. 13A: S250, S260, S270/S280).

When the detrack value is changed stepwise within the predeterminedrange (e.g., −10% to +10%/−8% to +8%) of numeric values including thereference value 0 (FIGS. 15, 16, and 17) of the detrack value, a dividedwidth of the detrack value is set to, for example, a value within arange from 0.5% to 5%, specifically, a value within a range from 1% to4% of the whole detrack values. If the divided width of the detrackvalue is a small divided width, for example, less than 0.5% of the wholedetrack values, since a large amount of data is to be acquired it isfeared that the time spent for the detrack adjustment may be prolonged.If the divided width of the detrack value is a great divided width, forexample, greater than 5% of the whole detrack values, since the numberof acquired data is insufficient, it is feared that the accurate detrackadjustment may not be performed. By setting the divided width of thedetrack value to a value within a range from 1% to 4% of whole thedetrack values, preferably, by setting the divided width of the detrackvalue to 2% of the whole detrack values, the time spent for the detrackadjustment is not so prolonged and the relatively accurate detrackadjustment is performed.

As shown in FIGS. 18 and 19, before there is performed the operation fordetecting the jitter value every time the detrack value is changedstepwise within the predetermined range of numeric values including thereference value 0 of the detrack value being centered, the jitter valueis detected based on the reference value 0 of the detrack value, and ifit is determined that the detected jitter value jitter(i_(b)o) based onthe reference value 0 of the detrack value is a small value equal to orsmaller than the predetermined jitter value jitter(i_(b)f), thereference value 0 of the detrack value is set as the optimum detrackvalue.

Specifically, when the detrack adjustment of the OBL 4 is performed forthe optical disc (M) (FIG. 1) and the optimum detrack value is set inthe optical disc apparatus 1, the jitter value is first detected basedon the reference value 0 (FIG. 18) of the detrack value: and if it isdetermined that the detected jitter value jitter(i_(b)o) based on thereference value 0 of the detrack value is a small value equal to orsmaller than the predetermined jitter value jitter(i_(b)f), thejitter-value detecting process is omitted without detecting each of thejitter values every time the detrack value is changed stepwise withinthe predetermined range of numeric values including the reference value0 of the detrack value; and the reference value 0 of the detrack valueis set as the optimum detrack value immediately after the detectingprocess of the jitter value jitter(i_(b)o) based on the reference value0 of the detrack value and the comparing and determining process betweenthe predetermined jitter value jitter(i_(b)f) and the jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value.

When the detrack value is ±0, if the jitter value jitter(i_(b)o) is asmall value equal to or smaller than the predetermined jitter valuejitter(i_(b)f), the optimum detrack value is set to ±0. If the opticaldisc M with good jitter characteristics is used, the stability of thetracking servo is prioritized.

By performing the detrack-value adjusting method of the optical discapparatus 1 (FIG. 1) as above, when the optical disc M with good jittercharacteristics is used, the detrack value is swiftly set and the OPU 2making up the optical disc apparatus 1 performs the stable trackingservo operation for the optical disc M. When the detrack adjustment ofthe OBL 4 is performed for the optical disc M and the optimum detrackvalue is set in the optical disc apparatus 1, the jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value isfirst detected (FIG. 13A: S220). As shown in FIG. 18, the optical disc M(FIG. 1): if it is determined that the jitter value jitter (i_(b)o)therefor based on the reference value 0 of the detrack value is a smallvalue equal to or smaller than the predetermined jitter valuejitter(i_(b)f); is considered as the optical disc M with good jittercharacteristics.

When reading the signal from the optical disc M with good jittercharacteristics: the jitter-value detecting/comparing and determiningprocesses (FIG. 13A: S240, FIG. 13B: S241 to S246, FIG. 13A: S250, S260)are omitted without detecting each of the jitter values every time thedetrack value is changed stepwise within the predetermined range ofnumeric values including the reference value 0 of the detrack value; andthe reference value 0 of the detrack value is set as the optimum detrackvalue in the optical disc apparatus 1 (FIG. 13A: S280) immediately afterthe detecting process (FIG. 13A: S220) of the jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value andthe comparing and determining process (FIG. 13A: S230) between thepredetermined jitter value jitter(i_(b)f) and the jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value.Therefore, the setting time of the detrack value is reduced in theoptical disc apparatus 1. When reading the signal from the optical discM with good jitter characteristics, since the reference value 0 of thedetrack value is set as the optimum detrack value in the optical discapparatus 1, the stable tracking servo operation is performed in the OPU2 without malfunction occurring in the tracking servo operation of theOPU 2.

When the detrack adjustment of the OBL 4 is performed for the opticaldisc M (FIG. 1) and the optimum detrack value is set in the optical discapparatus 1, the jitter value is first detected based on the referencevalue 0 (FIG. 19) of the detrack value: and if it is determined that thedetected jitter value jitter(i_(b)o) based on the reference value 0 ofthe detrack value is a small value equal to or smaller than thepredetermined jitter value jitter (i_(b)f), the jitter-value detectingprocess is omitted without detecting each of the jitter values everytime the detrack value is changed stepwise within the predeterminedrange of numeric values including the reference value 0 of the detrackvalue; and the reference value 0 of the detrack value is set as theoptimum detrack value immediately after the detecting process of thejitter value jitter(i_(b)o) based on the reference value 0 of thedetrack value and the comparing and determining process between thepredetermined jitter value jitter(i_(b)f) and the jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value.

When the detrack value is ±0, if the jitter value jitter(i_(b)o) is asmall value equal to or smaller than the predetermined jitter valuejitter(i_(b)f), the optimum detrack value is set to ±0. If the opticaldisc M with good jitter characteristics is used, the stability of thetracking servo is prioritized.

By performing the detrack-value adjusting method of the optical discapparatus 1 (FIG. 1) as above, when the optical disc M with good jittercharacteristics is used, the detrack value is swiftly set and the OPU 2making up the optical disc apparatus 1 performs the stable trackingservo operation for the optical disc M. When the detrack adjustment ofthe OBL 4 is performed for the optical disc M and the optimum detrackvalue is set in the optical disc apparatus 1, the jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value isfirst detected (FIG. 13A: S220). As shown in FIG. 19, the optical disc M(FIG. 1): if it is determined that the jitter value jitter (i_(b)o)therefor based on the reference value 0 of the detrack value is a smallvalue equal to or smaller than the predetermined jitter valuejitter(i_(b)f); is considered as the optical disc M with good jittercharacteristics. Alternatively, for example, as shown in FIG. 19, theoptical disc M (FIG. 1): if it is determined that all the jitter valuesbetween the maximum jitter value jitter(i_(b)max) therefor and theminimum jitter value jitter(i_(b)min) therefor are small values equal toor smaller than the predetermined jitter value jitter(i_(b)f); isconsidered as the optical disc M with good jitter characteristics.

When reading the signal from the optical disc M with good jittercharacteristics: the jitter-value detecting/comparing and determiningprocesses (FIG. 13A: S240, FIG. 13B: S241 to S246, FIG. 13A: S250, S260)are omitted without detecting each of the jitter values every time thedetrack value is changed stepwise within the predetermined range ofnumeric values including the reference value 0 of the detrack value; andthe reference value 0 of the detrack value is set as the optimum detrackvalue in the optical disc apparatus 1 (FIG. 13A: S280) immediately afterthe detecting process (FIG. 13A: S220) of the jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value andthe comparing and determining process (FIG. 13A: S230) between thepredetermined jitter value jitter(i_(b)f) and the jitter valuejitter(i_(b)o) based on the reference value 0 of the detrack value.Therefore, the setting time of the detrack value is reduced in theoptical disc apparatus 1. When reading the signal from the optical discM with good jitter characteristics, since the reference value 0 of thedetrack value is set as the optimum detrack value in the optical discapparatus 1, the stable tracking servo operation is performed in the OPU2 without malfunction occurring in the tracking servo operation of theOPU 2.

Since the detrack value ±0 is first measured and set, the measurementtime for detecting the jitter value can be reduced. It is possible toallow the optical disc apparatus 1 including the OPU 2 to perform thedetrack adjustment only for the optical disc (M) for which the jittervalue is presumed/determined as not good and the detection/check of eachof the jitter values is required. Since the detrack adjustment isperformed only for the optical disc (M) for which the jitter value ispresumed/determined as not good and the detection/check of each of thejitter values is required, the initial measurement time of the opticaldisc M with good jitter characteristics can be reduced in the OPU 2.Since the detrack value is set to ±0 for the optical disc M with goodjitter, the stable tracking servo can be performed for the optical discM with good jitter. Since the detrack value is set to ±0 for thetracking servo circuit 32 when the optical disc apparatus 1 is disposedwith the optical disc M for which the jitter value therefor is notsubstantially changed, no track skip occurs and the stable trackingservo can be performed.

As described above, in the detrack-value adjusting method of the opticaldisc apparatus 1, the jitter value is detected every time the detrackvalue is changed by the predetermined % within the predetermined rangecentering the reference value 0 of the detrack value, to perform theoperation of setting the optimum detrack value. Before such an operationis performed, the operation of detecting the jitter value is performedin the state where the detrack value is set to the reference detrackvalue defined as zero. If it is determined that the detected jittervalue jitter (i_(b)o) is a small value equal to or smaller than thepredetermined value jitter(i_(b)f), i.e., if it is determined that theoptical disc M has good reproduction characteristics, there is performedthe operation of setting the reference detrack value 0, as it is, as theoptimum detrack value in the optical disc apparatus 1.

If the jitter value jitter(i_(b)o) to be detected/set for thedetermining operation is detected as a small jitter value equal to orsmaller than, for example, a predetermined jitter value jitter(i_(b)f),the optical disc M is determined as a good disc, and the reproductionoperation can be performed without trouble even if the selectingoperation of the detrack value is not performed.

After the optical disc M with good jitter characteristics is completelydisposed in the optical disc apparatus 1, when performing the detrackadjustment of the OBL 4 in the optical disc apparatus 1 for the opticaldisc M with good jitter characteristics, the detrack adjustment isperformed within a time period from more than 0 second to substantially3 seconds, preferably, a time period from more than 0 second tosubstantially 1 second.

After the optical disc M with good jitter characteristics is completelydisposed in the optical disc apparatus 1, when performing the detrackadjustment of the OBL 4 for the optical disc M, the detrack adjustmentis performed within a time period from more than 0 second tosubstantially 3 seconds, preferably, a time period from more than 0second to substantially 1 second. Therefore, a situation is avoidedwhere one must wait for a long time due to the detrack adjustmentautomatically performed by the optical disc apparatus 1 from the timewhen the optical disc M is disposed in the optical disc apparatus 1 tothe time when the main data/information/signals of the optical disc Mare started to be read. When the optical disc M with good jittercharacteristics is disposed in the optical disc apparatus 1, the detrackadjustment in the optical disc apparatus 1 is swiftly completed in ashort time.

Description will then be made of a state when the track jump of the OPU2 is performed if the detrack value other than the reference value 0 isset.

First, the detrack adjustment of the optical disc apparatus 1 (FIG. 1)is performed. The detrack value is set to a numeric value other than thereference value 0 in this case. Before starting the track jump, thedetrack value is set to the reference value 0. The track jump operationis performed. After the track jump is completed, the detrack value isset back to the original numeric value other than the reference value 0.

Specifically describing the operation of the optical disc apparatus 1from the start to the end of the track jump process, if the optimumdetrack value is set to any one of biased numeric values other than thereference value 0 among the detrack values within the predeterminedrange (FIG. 13A: S270, FIG. 14, S291: NO, FIG. 15), when the OPU 2 isdriven to perform the track jump on the optical disc (M) (FIG. 1), thedetrack value is temporarily set to the reference value 0. After thedetrack value is temporarily set to the reference value 0 (FIG. 14:S292), the OPU 2 (FIG. 1) is driven to perform the track jump (FIG. 14:S293).

By setting the detrack value in the optical disc apparatus 1 (FIG. 1) asshown in the steps of S291 and S292 of FIG. 14, even if the optimumdetrack value is set to any one of biased numeric values (e.g., +6%)other than the reference value 0 of the detrack value among the detrackvalues within the predetermined range, the track jump of the OPU 2 onthe optical disc (M) is favorably performed. When the detrack adjustmentof the OPU 2 is performed for the optical disc (M), if the optimumdetrack value is set to a biased numeric value (+6%) other than thereference value 0, a track of the optical disc (M) may not be caughtwhen the track jump is performed by the OPU 2 on the optical disc (M).However, since the detrack value is temporarily set to the referencevalue 0 when the track jump is performed by the OPU 2, even if thedetrack value is set to a biased numeric value other than the referencevalue 0, the track jump becomes easily performed by the OPU 2 on theoptical disc (M) in a normal manner.

After the track jump of the OPU 2 is performed on the optical disc (M)(FIG. 1) (FIG. 14: S293) and the track jump operation is completed, thedetrack value is returned to the original biased numeric value (e.g.,+6%) other than the reference value 0 (FIG. 14: S295, FIG. 15). Sincethe optimum detrack value of the initial setting was set to the biasednumeric value other than the reference value 0 (FIG. 14, S294: NO, FIG.15), the detrack value is returned to the original biased numeric value(e.g., +6%) other than the reference value 0 after the track jump iscompleted (FIG. 14: S295).

Therefore, the optimum detrack value is again set in the optical discapparatus 1. When the track jump of the OPU 2 is not performed on theoptical disc (M), a biased numeric value other than the reference value0 of the detrack value is again set as the optimum detrack value in theoptical disc apparatus 1 and, therefore, the tracking adjustment of theOBL 2 of the OPU 2 is favorably performed for the optical disc (M).Since the detrack value other than the reference value 0 stored earlierin the second memory circuit 12 is again set as the optimum detrackvalue in the optical disc apparatus 1, the optimum detrack value isswiftly set again.

Description will then be made of a state when the track jump of the OPU2 is performed if the optimum detrack value is set to the referencevalue 0. Specifically describing the operation of the optical discapparatus 1 from the start to the end of the track jump process when theoptimum detrack value is set to the reference value 0, if the optimumdetrack value is set to the reference value 0 (FIG. 14, S291: YES, FIGS.16, 17, 18, and 19), the OPU 2 (FIG. 1) is driven to perform the trackjump without changing the detrack value (FIG. 14: S293) Since theoptimum detrack value continues to be set to the reference value 0, thetrack jump continues to be performed by the OPU 2 on the optical discM/(M) (FIG. 1) in a normal manner. Since the optimum detrack value ofthe initial setting was set to the reference value 0 (FIG. 14, S294:YES, FIGS. 16, 17, 18, and 19), the detrack value is not changed afterthe track jump is completed and the optimum detrack value is maintainedat the reference value 0.

The tilt-value adjusting method of the disc apparatus 1 will then bedescribed.

FIG. 20A is a flowchart of an embodiment of the tilt-value adjustingmethod of the disc apparatus; FIG. 20B is a flowchart of a jitter-valuedetecting process of the tilt-value adjusting method of the discapparatus; FIG. 21 is a flowchart of a track jump process whenperforming the tilt-value adjusting method of the disc apparatus; FIG.22 is a graphic representation of a relationship between the tilt valueand the jitter value; FIG. 23 is also a graphic representation of arelationship between the tilt value and the jitter value; FIG. 24 isalso a graphic representation of a relationship between the tilt valueand the jitter value; FIG. 25 is also a graphic representation of arelationship between the tilt value and the jitter value; and FIG. 26 isalso a graphic representation of a relationship between the tilt valueand the jitter value.

The tilt-value adjusting method of the optical disc apparatus 1 will bedescribed with reference to the figures in conjunction with flowchartsshown in FIGS. 20A, 20B, and 21.

The tilt adjusting method of the optical disc apparatus 1 based on thejitter value is performed as follows. For example, at the time ofreproduction of the reproduction/recording optical disc M (FIG. 1),there has already been completed the servo adjustment for the datareading, etc. In this case, for example, the offset adjustment of thefocus has already been performed. For example, the offset adjustment ofthe track has also already been performed. For example, in the opticaldisc apparatus 1, there is read a signal having the shape of S-curvesubstantially laid sideways with −50% to +50% of the tilt valuescentering a reference value 0. When the tilt adjusting method of theoptical disc apparatus 1 is performed, for example, a tilt adjustingmethod of the optical disc apparatus 1 including mechanical tiltadjustment is performed.

The optical disc apparatus 1 is used to perform the tilt adjustment ofthe OBL 4 for the signal face portion Ms of the optical disc M. Theoptical disc apparatus 1 is used to perform the tilt-value adjustingmethod in the optical disc apparatus 1.

For example, when the optical disc apparatus 1 is turned on,preparations are started for performing the tilt-value adjusting methodof the optical disc apparatus 1. When the optical disc apparatus 1 isturned on and the optical disc apparatus 1 is rendered in the power-onstate, for example, data such as various pieces of information are sentfrom the memory circuit 11 such as the ROM 11 to the system controlcircuit 10. At this point, various data, for example, a predeterminedjitter value jitter(i_(c)f) and a determination value jitter(i_(c)s) aresent to the system control circuit 10 and set in the system controlcircuit 10 (FIG. 20A: S310).

The tilt-value adjusting method of this optical disc apparatus 1(FIG. 1) is a tilt-value adjusting method of the optical disc apparatus1 that performs the tilt adjustment of the OBL 4 for the optical disc Mwith the use of the optical disc apparatus 1 including the OPU 2 havingthe OBL 4 by detecting the jitter value of the signal read from theoptical disc M and by adjusting the tilt value used for correcting theangular displacement of the OBL 4 relative to the signal face portion Msof the optical disc M when the OBL 4 of the OPU 2 is focused on thesignal face portion Ms of the optical disc M based on the detectedjitter value. The tilt-value setting process is performed as follows.

By disposing the optical disc M on the optical disc apparatus 1, theoperation is substantially started for setting the suitable tilt valuein the optical disc apparatus 1. First, a tilt voltage is applied to thetilt coil (TILT COIL) 73 to measure the jitter with the use of theoptical disc apparatus 1. When causing the optical disc apparatus 1 toperform the tilt-value adjusting method, the jitter is firstdetected/measured at the tilt value of ±0 (FIG. 20A: S320). At thispoint, for example, as shown in FIG. 25 or FIG. 26, if it is determinedthat a jitter value jitter(i_(c)o) at the tilt value of ±0 is a smallvalue equal to or smaller than a specified value jitter(i_(c)f) and theprogram in the CPU 10 determines that the optical disc M (FIG. 1) hasgood jitter characteristics (FIG. 20A, S330: NO), the tilt value is setto zero (FIG. 20A: S380) and the tilt adjustment is completed.

This optical disc apparatus 1 performs a different tilt-value adjustingmethod for each of the optical disc M with good jitter characteristicsand the optical disc (M) determined to have the jitter characteristicsthat are not good.

When the tilt-value adjusting method in the optical disc apparatus 1 isperformed with the use of the optical disc apparatus 1, for example, asshown in FIGS. 22, 23, and 24, jitter values are detected/measured asneeded. Specifically, in the case of the optical disc (M) for which: itis determined that the jitter value jitter(i_(c)o) at the tilt value of±0 is a value greater than the specified value jitter(i_(c)f); theprogram in the CPU 10 (FIG. 1) presumes/determines that the jittercharacteristics are not good; and it is also determined that each of thejitter values requires the detection/check, the following measurement isperformed. First, when reading the signal from the optical disc (M) todetect the jitter value, the tilt value within a predetermined range ischanged. Specifically, when reading the signal from the optical disc (M)to detect the jitter value, the tilt value is changed stepwise within apredetermined range of numeric values including the reference value 0 ofthe tilt value (FIGS. 22, 23, and 24) being centered (FIG. 20A: S340,FIG. 20B: S341 to S346). Every time the tilt value is changed stepwise,the jitter value is detected.

The operation of setting the tilt value is performed by the tilt-valuesetting circuit 23 in the state of performing the reproduction operationfor the signal recorded in the optical disc (M) (FIG. 1). In thetilt-value setting circuit 23, a value of the tilt value to be set ischanged in a stepwise of 2% from −8% to +8% relative to the referencevalue 0 (FIGS. 22, 23, and 24). At the same time, the jitter value ofthe reproduction signal is detected correspondingly to the tilt valuesby the jitter measurement circuit 9 to set the tilt value.

Specifically, while the tilt value is set in the tilt-value settingcircuit 23 to a value lower than the reference value 0 by substantially−8%, the reproduction operation is performed for the signal recorded inthe optical disc (M) to detect the jitter value included in thereproduction signal with the jitter measurement circuit 9. The jittervalue detected in this way is stored in the memory circuit 12 such asthe RAM 12 along with the tilt value.

As the tilt value is changed in a stepwise of 2% from −8% to +8%relative to the reference value 0, the jitter value corresponding to thetilt value is detected and the jitter value is stored in the memorycircuit 12 along with the tilt value. The operation is repeatedlyperformed.

When the operation is started for setting the tilt value in the opticaldisc apparatus 1, in the case of the optical disc (M) for which it isdetermined that the jitter values require detection/check during theprocess of the tilt adjusting method of the optical disc apparatus 1,the operation of detecting the jitter value is first performed each timethe tilt value is changed within a predetermined range (FIG. 20A: S340,FIG. 20B: S341 to S346). The predetermined range is defined, forexample, if the tilt value 0 is defined as a reference value, as thetilt values from −10% to +10% to be set in the tilt-value settingcircuit 23 relative to the reference value (FIGS. 22, 23, and 24). Thepreferable predetermined range of tilt values is defined, for example,if the tilt value 0 is defined as a reference value, as a range from −8%to +8% to be set in the tilt-value setting circuit 23 relative to thereference value.

For example, if the tilt value is set to a value smaller than the −10%value, the tilt function may not work normally. Alternatively, forexample, if the tilt value is set to a value greater than the +10%value, the tilt function may not work normally. Therefore, the tiltvalues from −10% to +10% centering the reference value 0 of the tiltvalue may be set in the tilt-value setting circuit 23. Preferably, thetilt function works normally by setting the tilt values from −8% to +8%centering the reference value 0 of the tilt value in the tilt-valuesetting circuit 23.

For example, in the case of the optical disc (M) (FIG. 1) for which: itis determined that the jitter value jitter(i_(c)o) at the referencevalue 0 of the tilt value (FIGS. 22, 23, and 24) is a value greater thanthe specified value jitter(i_(c)f); it is presumed/determined that thejitter value is not good; and it is also determined that each of thejitter values requires detection/check, the following process isperformed under the control of the program in the CPU 10. The followingprocess is performed by the CPU 10 and the second memory circuit 12.

First, an initial value is set by the program in the CPU 10 to seti_(c)=−4 (FIG. 20B: S341). For example, a value of “TILT=2%×i_(c)” isset (SET) (S342). The jitter value is measured by the OPU 2 (S343) andthe result is stored in the second memory circuit 12 as “jitter(i_(c))”(S344).

The “i_(c)” is incremented by the program in the CPU 10 (S341, S342 toS346).

In the case of “i_(c)<5” (S346: NO), a value of “TILT=2%×i_(c)” is set(S342) and the jitter is measured again by the OPU 2 (S343) to store theresult in the second memory circuit 12 as “jitter(i_(c))” (S344). In thecase of “i_(c)≧5” (S346: YES), a minimum value is obtained from“jitter(i_(c))”, and “i_(c)” at this point is defined as “i_(c)min”(FIG. 20A: S350). In the case of “i_(c)≧5” (FIG. 20B, S346: YES), amaximum value is obtained from “jitter (i_(c))”, and “i_(c)” at thispoint is defined as “i_(c)max” (FIG. 20A: S350).

The optimum tilt value is then set based on a difference valuejitter(i_(c)d) between the maximum jitter value jitter(i_(c)max) and theminimum jitter value jitter(i_(c)min) of the detected jitter values(S360).

The tilt value is changed within the predetermined range: the detectionoperation of each of the jitter values is performed (FIG. 20A: S340,FIG. 20B: S341 to S346); and the maximum jitter value jitter(i_(c)max)and the minimum jitter value jitter(i_(c)min) are selected from thedetected jitter values (FIG. 20A: S350).

After the selection setting operation at the step of S350 is performed,there is performed a determination operation which determines whether[jitter(i_(c)max)−jitter(i_(c)min)>jitter(i_(c)s)] is satisfied (S360:YES) or [jitter(i_(c)max)−jitter(i_(c)min)>jitter(i_(c)s)] is notsatisfied (S360: NO). If it is determined that[jitter(i_(c)max)−jitter(i_(c)min)>jitter(i_(c)s)] is satisfied at thestep of S360 (S360: YES), the tilt value corresponding to the minimumjitter value jitter(i_(c)min) is set as the optimum tilt value (S370).Alternatively, if it is determined that[jitter(i_(c)max)−jitter(i_(c)min)>jitter(i_(c)s)] is not satisfied atthe step of S360 (S360: NO), the reference value 0 of the tilt value isset as the optimum tilt value (S380).

The optimum tilt value is set in the optical disc apparatus 1 byperforming the tilt-value adjusting method of the optical disc apparatus1 as above. The jitter value is detected as needed every time the tiltvalue is changed stepwise within the predetermined range of numericvalues including the reference value 0 of the tilt value and beingcentered so that the optimum tilt value is set based on the differencevalue jitter(i_(c)d) between the maximum jitter value jitter(i_(c)max)and the minimum jitter value jitter(i_(c)min) of the detected jittervalues. Therefore, the optimum tilt value is set in the optical discapparatus 1. Since the optimum tilt value is set in the optical discapparatus 1, the OPU 2 performs the stable tilt operation for theoptical disc M. The tilt value setting operation can easily be performedin the optical disc apparatus 1.

After the optical disc (M) is completely disposed in the optical discapparatus 1, when reading each of the signals from the optical disc (M)and detecting each of the jitter values to perform the tilt adjustmentof the OBL 4 for the optical disc (M), the tilt adjustment is performedwithin a time period from more than 0 second to substantially 20seconds. More specifically, after the optical disc (M) is completelydisposed in the optical disc apparatus 1, when the tilt value is changedstepwise within the predetermined range of numeric values including thereference value 0 (FIGS. 22, 23, and 24) of the tilt value and beingcentered (FIG. 20A: S340, FIG. 20B: S341 to S346) to read each of thesignals from the optical disc (M) (FIG. 1) and detect each of the jittervalues, so that the optimum tilt-value adjustment of the OBL 4 for theoptical disc (M) (FIG. 1) is performed based on the difference valuejitter (i_(c)d) between the maximum jitter value jitter(i_(c)max) (FIGS.22, 23, and 24) and the minimum jitter value jitter(i_(c)min) of thedetected jitter values (FIG. 20A: S360). The tilt adjustment ispreferably completed within a time period from more than 0 second tosubstantially 15 seconds.

Since the time spent for the tilt-value adjusting method of the opticaldisc apparatus 1 is set to a short time, there is swiftly completed thesetting process when the tilt adjustment is performed in the opticaldisc apparatus 1 without waiting for a long time due to the tiltadjustment. After the optical disc (M) is completely disposed in theoptical disc apparatus 1, when the tilt value is changed stepwise withinthe predetermined range of numeric values including the reference value0 of the tilt value being centered, to read each of the signals from theoptical disc (M) and detect each of the jitter values to perform thetilt adjustment of the OBL 4 for the optical disc (M) based on thedifference value jitter(i_(c)d) between the maximum jitter valuejitter(i_(c)max) and the minimum jitter value jitter(i_(c)min) of thedetected jitter values, the tilt adjustment is performed within a timeperiod from more than 0 second to substantially 20 seconds, preferably,within a time period from more than 0 second to substantially 15seconds. Therefore, a situation is avoided where one must wait for avery long time due to the tilt adjustment automatically performed by theoptical disc apparatus 1 from the time when the optical disc (M) isdisposed in the optical disc apparatus 1 to the time when the maindata/information/signals of the optical disc (M) are started to be read.

FIG. 22 is a characteristic view of a relationship between the jittervalue and the tilt value when it is determined in the CPU 10 (FIG. 1)that [jitter(i_(c)max)−jitter(i_(c)min)>jitter(i_(c)s)] is satisfied(FIG. 20A, S360: YES).

When performing the tilt adjustment of the OBL 4 for the optical disc(M) (FIG. 1), if it is determined that the difference valuejitter(i_(c)d) between the maximum jitter value jitter (i_(c)max) andthe minimum jitter value jitter(i_(c)min) is a value greater than thepredetermined value jitter(i_(c)s) as shown in FIG. 22, the tilt valuecorresponding to the minimum jitter value jitter(i_(c)min) is set as theoptimum tilt value.

The minimum jitter value jitter(i_(c)min) is smaller than the jittervalue jitter(i_(c)f) that is smaller than the maximum jitter valuejitter(i_(c)max) by the determination value jitter(i_(c)s), for example.In such a case, in the optical disc apparatus 1, there is performed theoperation of setting the tilt value corresponding to the minimum jittervalue jitter(i_(c)min), i.e., the tilt value greater than the referencevalue 0 by +6% as the optimum tilt value with the tilt-value settingcircuit 23.

The program in the CPU 10 (FIG. 1) performs the next setting based onthe value of [jitter(i_(c)max)−jitter(i_(c)min)]. If the value of[jitter(i_(c)max)−jitter(i_(c)min)] exceeds a certain valuejitter(i_(c)s), “TILT” is set to “2%×i_(c)min”, for example. The tiltadjustment is completed in this way.

When the tilt-value setting operation is performed as above, the tiltvalue greater than the reference tilt value 0 by +6% is set in thetilt-value setting circuit 23, and the tilt operation of the tilt-valuesetting circuit 23 is performed centering the set tilt value.

By performing the tilt-value adjusting method of the optical discapparatus 1 as above, the OPU 2 making up the optical disc apparatus 1performs the stable tilt operation for the optical disc (M). The opticaldisc (M): when it is determined that the difference value jitter(i_(c)d)between the maximum jitter value jitter(i_(c)max) therefor and theminimum jitter value jitter(i_(c)min) therefor is a value greater thanthe predetermined value jitter(i_(c)s); is considered as the opticaldisc (M) with poor jitter characteristics. Since the tilt valuecorresponding to the minimum jitter value jitter(i_(c)min) is set as theoptimum tilt value when reading a signal from the optical disc (M) withthe poor jitter characteristics, the stable tilt operation is performedin the OPU 2.

If it is determined that[jitter(i_(c)max)−jitter(i_(c)min)>jitter(i_(c)s)] is not satisfied atthe step of S360 shown in FIG. 20A (S360: NO), the reference tilt value0 is set as the optimum tilt value (S380).

FIG. 23 is a characteristic view of a relationship between the jittervalue and the tilt value when it is determined in the CPU 10 (FIG. 1)that [jitter(i_(c)max)−jitter(i_(c)min)>jitter(i_(c)s)] is not satisfied(FIG. 20A, S360: NO).

When performing the tilt adjustment of the OBL 4 for the optical disc(M) (FIG. 1), if it is determined that the difference valuejitter(i_(c)d) between the maximum jitter value jitter (i_(c)max) andthe minimum jitter value jitter(i_(c)min) is a small value equal to orsmaller than the predetermined value jitter(is) as shown in FIG. 23, thereference value 0 of the tilt value is set as the optimum tilt value. Ifthe maximum value−minimum value (MAX−MIN) of the jitter values is equalto or smaller than a certain value, the tilt value is set to ±0. Forexample, when the jitter values with a wave shape shown in FIG. 23 aredetected, if it is determined that the jitter value jitter(i_(c)o) atthe reference value 0 of the tilt value is a value greater than thepredetermined jitter value jitter(i_(c)f) and that the difference valuejitter(i_(c)d) between the maximum jitter value jitter(i_(c)max) and theminimum jitter value jitter(i_(c)min) is a small value equal to orsmaller than the predetermined value jitter (i_(c)s), the tilt value isset to ±0. Alternatively, for example, when the jitter values with awave shape shown in FIG. 23 are detected, if it is determined that allthe jitter values are values greater than the predetermined jitter valuejitter(i_(c)f) and that the difference value jitter(i_(c)d) between themaximum jitter value jitter(i_(c)max) and the minimum jitter valuejitter(i_(c)min) is a small value equal to or smaller than thepredetermined value jitter(i_(c)s), the tilt value is set to ±0.

The minimum jitter value jitter(i_(c)min) is greater than the jittervalue jitter(i_(c)f) that is smaller than the maximum jitter valuejitter(i_(c)max) by the determination value jitter(i_(c)s), for example.In such a case, since the changes in the jitter values are small, thereis performed the operation of setting the reference tilt value as theoptimum tilt value for the tilt-value setting circuit 23 in the opticaldisc apparatus 1.

In the program in the CPU 10 (FIG. 1), the next setting is performedbased on the value of [jitter(i_(c)max)−jitter(i_(c)min)] If the valueof [jitter(i_(c)max)−jitter(i_(c)min)] is equal to or smaller than acertain value jitter(i_(c)s), “TILT” is set to 0. The tilt adjustment iscompleted in this way.

When the tilt-value setting operation is performed as above, the tiltoperation of the tilt-value setting circuit 23 is performed centeringthe reference tilt value 0. Since the tilt setting/operation isperformed centering the reference tilt value 0, the tilt control canstably be performed in the OPU 2.

By performing the tilt-value adjusting method of the optical discapparatus 1 as above, the OPU 2 making up the optical disc apparatus 1performs the stable tilt operation for the optical disc M. The opticaldisc M: when it is determined that the difference value jitter(i_(c)d)between the maximum jitter value jitter(i_(c)max) therefor and theminimum jitter value jitter(i_(c)min) therefor is a small value equal toor smaller than the predetermined value jitter(i_(c)s); is considered asthe optical disc M with relatively good jitter characteristics. Sincethe reference value 0 of the tilt value is set as the optimum tilt valuein the optical disc apparatus 1 when reading a signal from the opticaldisc M with the relatively good jitter characteristics, the stable tiltoperation is performed in the OPU 2 without malfunction occurring in thetilt operation of the OPU 2. The setting of the tilt value can easily beperformed in the optical disc apparatus 1.

When performing the tilt adjustment of the OBL 4 for the optical disc(M) (FIG. 1), if it is determined that the difference valuejitter(i_(c)d) between the maximum jitter value jitter(i_(c)max) and theminimum jitter value jitter(i_(c)min) is a small value equal to orsmaller than the predetermined value jitter(i_(c)s) as shown in FIG. 24,the reference value 0 of the tilt value is set as the optimum tiltvalue. If the value of maximum value−minimum value (MAX−MIN) of thejitter values is equal to or smaller than a certain value, the tiltvalue is set to ±0. For example, when the jitter values with a waveshape shown in FIG. 24 are detected, if it is determined that the jittervalue jitter(i_(c)o) at the reference value 0 of the tilt value is avalue greater than the predetermined jitter value jitter(i_(c)f) andthat the difference value jitter(i_(c)d) between the maximum jittervalue jitter(i_(c)max) and the minimum jitter value jitter(i_(c)min) isa small value equal to or smaller than the predetermined valuejitter(i_(c)s), the tilt value is set to ±0. In such a case, since thechanges in the jitter values are small, the optical disc apparatus 1performs the operation of setting the reference tilt value as theoptimum tilt value in the tilt-value setting circuit 23.

In the program in the CPU 10 (FIG. 1), the next setting is performedbased on the value of [jitter(i_(c)max)−jitter(i_(c)min)] If the valueof [jitter(i_(c)max)−jitter(i_(c)min)] is equal to or smaller than acertain value jitter(i_(c)s), “TILT” is set to 0. The tilt adjustment iscompleted in this way.

When the tilt-value setting operation is performed as above, the tiltoperation of the tilt-value setting circuit 23 is performed with thereference tilt value 0 being centered. Since the tilt setting/operationis performed with the reference tilt value 0 being centered, the tiltcontrol can stably be performed in the OPU 2.

By performing the tilt-value adjusting method of the optical discapparatus 1 as above, the OPU 2 making up the optical disc apparatus 1performs the stable tilt operation for the optical disc M. The opticaldisc M: when it is determined that the difference value jitter(i_(c)d)between the maximum jitter value jitter(i_(c)max) therefor and theminimum jitter value jitter(i_(c)min) therefor is a small value equal toor smaller than the predetermined value jitter(i_(c)s); is considered asthe optical disc M with relatively good jitter characteristics. Sincethe reference value 0 of the tilt value is set as the optimum tilt valuein the optical disc apparatus 1 when reading a signal from the opticaldisc M with the relatively good jitter characteristics, the stable tiltoperation is performed in the OPU 2 without malfunction occurring in thetilt operation of the OPU 2. The setting of the tilt value can easily beperformed in the optical disc apparatus 1.

After the optical disc (M) is completely disposed in the optical discapparatus 1, each of the signals is read from the optical disc (M) andeach of the jitter values is detected, to perform the tilt adjustment ofthe OBL 4 for the optical disc (M). The tilt adjustment is performedwithin a time period from more than 0 second to substantially 15seconds. More specifically, after the optical disc (M) is completelydisposed in the optical disc apparatus 1, when the tilt value is changedstepwise within the predetermined range of numeric values including thereference value 0 (FIGS. 22, 23, and 24) of the tilt value beingcentered (FIG. 20A: S340, FIG. 20B: S341 to S346) to read each of thesignals from the optical disc (M) (FIG. 1) and detect each of the jittervalues, so that the optimum tilt-value adjustment of the OBL 4 for theoptical disc (M) (FIG. 1) is performed based on the difference valuejitter(i_(c)d) between the maximum jitter value jitter(i_(c)max) (FIGS.22, 23, and 24) and the minimum jitter value jitter(i_(c)min) of thedetected jitter values (FIG. 20A: S360). The above tilt adjustment ispreferably completed within a time period from more than 0 second tosubstantially 10 seconds.

Since the time spent for the tilt-value adjusting method of the opticaldisc apparatus 1 is set to a short time as above, there is swiftlycompleted the setting process when the tilt adjustment is performed inthe optical disc apparatus 1 without waiting for a long time due to thetilt adjustment. After the optical disc (M) is completely disposed inthe optical disc apparatus 1, when the tilt value is changed stepwisewithin the predetermined range of numeric values including the referencevalue 0 of the tilt value being centered, to read each of the signalsfrom the optical disc (M) and detect each of the jitter values so thatthe tilt adjustment of the OBL 4 for the optical disc (M) is performedbased on the difference value jitter(i_(c)d) between the maximum jittervalue jitter(i_(c)max) and the minimum jitter value jitter(i_(c)min) ofthe detected jitter values, the tilt adjustment is performed within atime period from more than 0 second to substantially 15 seconds,preferably, within a time period from more than 0 second tosubstantially 10 seconds. Therefore, a situation is avoided where onemust wait for a very long time due to the tilt adjustment automaticallyperformed by the optical disc apparatus 1 from the time when the opticaldisc (M) is disposed in the optical disc apparatus 1 to the time whenthe main data/information/signals of the optical disc (M) are started tobe read.

As described above, when the tilt adjustment of the OBL 4 is performedfor the optical disc (M) (FIG. 1) and the optimum tilt value is set inthe optical disc apparatus 1, the jitter value is first detected basedon the reference value 0 (FIGS. 22, 23, and 24) of the tilt value, andif it is determined that the detected jitter value jitter(i_(c)o) basedon the reference value 0 of the tilt value is a value greater than thepredetermined jitter value jitter(i_(c)f), a jitter-value detectingprocess is then executed to detect the jitter value every time the tiltvalue is changed stepwise within the predetermined range (e.g., −8% to+8%/−10% to +10%) of numeric values including the reference value 0 ofthe tilt value.

The optimum tilt value is set in the optical disc apparatus 1 byperforming the tilt-value adjusting method of the optical disc apparatus1 (FIG. 1) as above. When the tilt adjustment of the OBL 4 is performedfor the optical disc (M) and the optimum tilt value is set in theoptical disc apparatus 1, the jitter value jitter(i_(c)o) based on thereference value 0 of the tilt value is first detected (FIG. 20A: S320).As shown in FIGS. 22, 23, and 24, the optical disc (M) (FIG. 1): if itis determined that the jitter value jitter(i_(c)o) therefor based on thereference value 0 of the tilt value is a value greater than thepredetermined jitter value jitter(i_(c)f); is considered as the opticaldisc (M) in need of detecting/checking each of the jitter valuescorresponding to each of the tilt values. As shown in FIG. 20A, if it isdetermined that the jitter value jitter(i_(c)o) based on the referencevalue 0 of the tilt value is a value greater than the predeterminedjitter value jitter(i_(c)f) (S330: YES), there are then performed thejitter-value detecting/comparing and determining/optimum value settingprocesses in which: each of the jitter values is detected every time thetilt value is changed stepwise within the predetermined range (e.g., −8%to +8%/−10% to +10%) of numeric values including the reference value 0of the tilt value (FIG. 20A: S340, FIG. 20B: S341 to S346); and theoptimum tilt value is set based on the difference value jitter(i_(c)d)between the maximum jitter value jitter(i_(c)max) and the minimum jittervalue jitter(i_(c)min) of the detected jitter values (FIG. 20A: S340,FIG. 20B: S341 to S346, FIG. 20A: S350, S360, S370/S380).

When the tilt value is changed stepwise within the predetermined range(e.g., −10% to +10%/−8% to +8%) of numeric values including thereference value 0 (FIGS. 22, 23, and 24) of the tilt value, a dividedwidth of the tilt value is set to, for example, a value within a rangefrom 0.5% to 5%, specifically, a value within a range from 1% to 4% ofwhole the tilt values. If the divided width of the tilt value is a smalldivided width, for example, less than 0.5% of the whole tilt values,since a large amount of data is to be acquired it is feared that thetime spent for the tilt adjustment may be prolonged. If the dividedwidth of the tilt value is a great divided width, for example, greaterthan 5% of the whole tilt values, the accurate tilt adjustment may notbe performed since the number of acquired data is insufficient. Bysetting the divided width of the tilt value to a value within a rangefrom 1% to 4% of the whole tilt values, preferably, by setting thedivided width of the tilt value to 2% of the whole tilt values, the timespent for the tilt adjustment is not so prolonged and the relativelyaccurate tilt adjustment is performed.

As shown in FIGS. 25 and 26, before there is performed the operation fordetecting the jitter value every time the tilt value is changed stepwisewithin the predetermined range of numeric values including the referencevalue 0 of the tilt value being centered, the jitter value is detectedbased on the reference value 0 of the tilt value, and if it isdetermined that the detected jitter value jitter(i_(c)o) based on thereference value 0 of the tilt value is a small value equal to or smallerthan the predetermined jitter value jitter(i_(c)f), the reference value0 of the tilt value is set as the optimum tilt value.

Specifically, when the tilt adjustment of the OBL 4 is performed for theoptical disc (M) (FIG. 1) and the optimum tilt value is set in theoptical disc apparatus 1, the jitter value is first detected based onthe reference value 0 (FIG. 25) of the tilt value: and if it isdetermined that the detected jitter value jitter(i_(c)o) based on thereference value 0 of the tilt value is a small value equal to or smallerthan the predetermined jitter value jitter(i_(c)f), the jitter-valuedetecting process is omitted without detecting each of the jitter valuesevery time the tilt value is changed stepwise within the predeterminedrange of numeric values including the reference value 0 of the tiltvalue; and the reference value 0 of the tilt value is set as the optimumtilt value immediately after the detecting process of the jitter valuejitter(i_(c)o) based on the reference value 0 of the tilt value and thecomparing and determining process between the predetermined jitter valuejitter(i_(c)f) and the jitter value jitter(i_(c)o) based on thereference value 0 of the tilt value.

When the tilt value is ±0, if the jitter value jitter(i_(c)o) is a smallvalue equal to or smaller than the predetermined jitter valuejitter(i_(c)f), the optimum tilt value is set to ±0. If the optical discM with good jitter characteristics is used, the stability of the tiltoperation is prioritized.

By performing the tilt-value adjusting method of the optical discapparatus 1 (FIG. 1) as above, when the optical disc M with good jittercharacteristics is used, the tilt value is swiftly set and the OPU 2making up the optical disc apparatus 1 performs the stable tiltoperation for the optical disc M. When the tilt adjustment of the OBL 4is performed for the optical disc M and the optimum tilt value is set inthe optical disc apparatus 1, the jitter value jitter(i_(c)o) based onthe reference value 0 of the tilt value is first detected (FIG. 20A:S320). As shown in FIG. 25, the optical disc M (FIG. 1): if it isdetermined that the jitter value jitter(i_(c)o) therefor based on thereference value 0 of the tilt value is a small value equal to or smallerthan the predetermined jitter value jitter(i_(c)f); is considered as theoptical disc M with good jitter characteristics.

When reading the signal from the optical disc M with good jittercharacteristics: the jitter-value detecting/comparing and determiningprocesses (FIG. 20A: S340, FIG. 20B: S341 to S346, FIG. 20A: S350, S360)are omitted without detecting each of the jitter values every time thetilt value is changed stepwise within the predetermined range of numericvalues including the reference value 0 of the tilt value; and thereference value 0 of the tilt value is set as the optimum tilt value inthe optical disc apparatus 1 (FIG. 20A: S380) immediately after thedetecting process (FIG. 20A: S320) of the jitter value jitter(i_(c)o)based on the reference value 0 of the tilt value and the comparing anddetermining process (FIG. 20A: S330) between the predetermined jittervalue jitter(i_(c)f) and the jitter value jitter(i_(c)o) based on thereference value 0 of the tilt value. Therefore, the setting time of thetilt value is reduced in the optical disc apparatus 1. When reading thesignal from the optical disc M with good jitter characteristics, sincethe reference value 0 of the tilt value is set as the optimum tilt valuein the optical disc apparatus 1, the stable tilt operation is performedin the OPU 2 without malfunction occurring in the tilt operation of theOPU 2.

When the tilt adjustment of the OBL 4 is performed for the optical discM (FIG. 1) and the optimum tilt value is set in the optical discapparatus 1, the jitter value is first detected based on the referencevalue 0 (FIG. 26) of the tilt value: and if it is determined that thedetected jitter value jitter(i_(c)o) based on the reference value 0 ofthe tilt value is a small value equal to or smaller than thepredetermined jitter value jitter(i_(c)f), the jitter-value detectingprocess is omitted without detecting each of the jitter values everytime the tilt value is changed stepwise within the predetermined rangeof numeric values including the reference value 0 of the tilt value; andthe reference value 0 of the tilt value is set as the optimum tilt valueimmediately after the detecting process of the jitter valuejitter(i_(c)o) based on the reference value 0 of the tilt value and thecomparing and determining process between the predetermined jitter valuejitter(i_(c)f) and the jitter value jitter(i_(c)o) based on thereference value 0 of the tilt value.

When the tilt value is ±0, if the jitter value jitter(i_(c)o) is a smallvalue equal to or smaller than the predetermined jitter valuejitter(i_(c)f), the optimum tilt value is set to ±0. If the optical discM with good jitter characteristics is used, the stability of the tiltoperation is prioritized.

By performing the tilt-value adjusting method of the optical discapparatus 1 (FIG. 1) as above, when the optical disc M with good jittercharacteristics is used, the tilt value is swiftly set and the OPU 2making up the optical disc apparatus 1 performs the stable tiltoperation for the optical disc M. When the tilt adjustment of the OBL 4is performed for the optical disc M and the optimum tilt value is set inthe optical disc apparatus 1, the jitter value jitter(i_(c)o) is firstdetected based on the reference value 0 of the tilt value (FIG. 20A:S320). As shown in FIG. 26, the optical disc M (FIG. 1): if it isdetermined that the jitter value jitter(i_(c)o) therefor based on thereference value 0 of the tilt value is a small value equal to or smallerthan the predetermined jitter value jitter(i_(c)f); is considered as theoptical disc M with good jitter characteristics. Alternatively, forexample, as shown in FIG. 26, the optical disc M (FIG. 1): if it isdetermined that all the jitter values between the maximum jitter valuejitter (i_(c)max) and the minimum jitter value jitter(i_(c)min) aresmall values equal to or smaller than the predetermined jitter valuejitter(i_(c)f); is considered as the optical disc M with good jittercharacteristics.

When reading the signal from the optical disc M with good jittercharacteristics: the jitter-value detecting/comparing and determiningprocesses (FIG. 20A: S340, FIG. 20B: S341 to S346, FIG. 20A: S350, S360)are omitted without detecting each of the jitter values every time thetilt value is changed stepwise within the predetermined range of numericvalues including the reference value 0 of the tilt value; and thereference value 0 of the tilt value is set as the optimum tilt value inthe optical disc apparatus 1 (FIG. 20A: S380) immediately after thedetecting process (FIG. 20A: S320) of the jitter value jitter(i_(c)o)based on the reference value 0 of the tilt value and the comparing anddetermining process (FIG. 20A: S330) between the predetermined jittervalue jitter(i_(c)f) and the jitter value jitter(i_(c)o) based on thereference value 0 of the tilt value. Therefore, the setting time of thetilt value is reduced in the optical disc apparatus 1. When reading thesignal from the optical disc M with good jitter characteristics, sincethe reference value 0 of the tilt value is set as the optimum tilt valuein the optical disc apparatus 1, the stable tilt operation is performedin the OPU 2 without malfunction occurring in the tilt operation of theOPU 2.

Since the tilt value ±0 is first measured and set, the measurement timefor detecting the jitter value can be reduced. It is possible to allowthe optical disc apparatus 1 including the OPU 2 to perform the tiltadjustment only for the optical disc (M) for which the jitter value ispresumed/determined as not good and the detection/check of each of thejitter values is required. Since the tilt adjustment is performed onlyfor the optical disc (M) for which the jitter value ispresumed/determined as not good and the detection/check of each of thejitter values is required, the initial measurement time of the opticaldisc M with good jitter characteristics can be reduced in the OPU 2.Since the tilt value is set to ±0 for the optical disc M with goodjitter, the stable tilt setting can be performed for the optical disc Mwith good jitter. Since the tilt value is set to ±0 in the tilt-valuesetting circuit 23 when the optical disc apparatus 1 is disposed withthe optical disc M for which the jitter value therefor is notsubstantially changed, no servo failure occurs and the stable tiltoperation can be performed.

As described above, in the tilt-value adjusting method of the opticaldisc apparatus 1, the jitter value is detected every time the tilt valueis changed by the predetermined % within the predetermined rangecentering the reference value 0 of the tilt value, to perform theoperation of setting the optimum tilt value. Before such an operation isperformed, the operation of detecting the jitter value is performed inthe state where the tilt value is set to the reference tilt valuedefined as zero. If it is determined that the detected jitter valuejitter(i_(c)o) is a small value equal to or smaller than thepredetermined value jitter(i_(c)f), i.e., if it is determined that theoptical disc M has good reproduction characteristics, there is performedthe operation of setting the reference tilt value 0, as it is, as theoptimum tilt value in the optical disc apparatus 1.

If the jitter value jitter(i_(c)o) to be detected/set for thedetermining operation is detected as a small jitter value equal to orsmaller than, for example, a predetermined jitter value jitter(i_(c)f),the optical disc M is determined as a good disc, and the reproductionoperation can be performed without trouble even if the selectingoperation of the tilt value is not performed.

After the optical disc M with good jitter characteristics is completelydisposed in the optical disc apparatus 1, when performing the tiltadjustment of the OBL 4 in the optical disc apparatus 1 for the opticaldisc M with good jitter characteristics, the tilt adjustment isperformed within a time period from more than 0 second to substantially3 seconds, preferably, a time period from more than 0 second tosubstantially 1 second.

After the optical disc M with good jitter characteristics is completelydisposed in the optical disc apparatus 1, when performing the tiltadjustment of the OBL 4 for the optical disc M, the tilt adjustment isperformed within a time period from more than 0 second to substantially3 seconds, preferably, a time period from more than 0 second tosubstantially 1 second. Therefore, a situation is avoided where one mustwait for a long waiting time is not generated due to the tilt adjustmentautomatically performed by the optical disc apparatus 1 from the timewhen the optical disc M is disposed in the optical disc apparatus 1 tothe time when the main data/information/signals of the optical disc Mare started to be read. When the optical disc M with good jittercharacteristics is disposed in the optical disc apparatus 1, the tiltadjustment in the optical disc apparatus 1 is swiftly completed in ashort time.

Description will then be made of a state when the track jump of the OPU2 is performed if the tilt value other than the reference value 0 isset.

First, the tilt adjustment of the optical disc apparatus 1 (FIG. 1) isperformed. The tilt value is set to a numeric value other than thereference value 0 in this case. Before starting the track jump, the tiltvalue is set to the reference value 0. The track jump operation isperformed. After the track jump is completed, the tilt value is set tothe original numeric value other than the reference value 0.

Specifically describing the operation of the optical disc apparatus 1from the start to the end of the track jump process, if the optimum tiltvalue is set to any one of biased numeric values other than thereference value 0 among the tilt values within the predetermined range(FIG. 20A: S370, FIG. 21, S391: NO, FIG. 22), when the OPU 2 is drivento perform the track jump on the optical disc (M) (FIG. 1), the tiltvalue is temporarily set to the reference value 0. After the tilt valueis temporarily set to the reference value 0 (FIG. 21: S392), the OPU 2(FIG. 1) is driven to perform the track jump (FIG. 21: S393).

By setting the tilt value in the optical disc apparatus 1 (FIG. 1) asshown in the steps of S391 and S392 of FIG. 21, even if the optimum tiltvalue is set to any one of biased numeric values (e.g., +6%) other thanthe reference value 0 of the tilt value among the tilt values within thepredetermined range, the track jump of the OPU 2 on the optical disc (M)is favorably performed. When the tilt adjustment of the OPU 2 isperformed for the optical disc (M), if the optimum tilt value is set toa biased numeric value (+6%) other than the reference value 0, the servofailure tends to occur in the OPU 2 when the track jump is performed bythe OPU 2 on the optical disc (M). However, since the tilt value istemporarily set to the reference value 0 when the track jump isperformed by the OPU 2, even if the tilt value is set to a biasednumeric value other than the reference value 0, the track jump becomesmore easily performed by the OPU 2 on the optical disc (M) in a normalmanner.

After the track jump of the OPU 2 is performed on the optical disc (M)(FIG. 1) (FIG. 21: S393) and the track jump operation is completed, thetilt value is returned to the original biased numeric value (e.g., +6%)other than the reference value 0 (FIG. 21: S395, FIG. 22). Since theoptimum tilt value of the initial setting was set to the biased numericvalue other than the reference value 0 (FIG. 21, S394: NO, FIG. 22), thetilt value is returned to the original biased numeric value (e.g., +6%)other than the reference value 0 after the track jump is completed (FIG.21: S395).

Therefore, the optimum tilt value is again set in the optical discapparatus 1. When the track jump of the OPU 2 is not performed on theoptical disc (M), a biased numeric value other than the reference value0 of the tilt value is again set as the optimum tilt value in theoptical disc apparatus 1 and, therefore, the tilt adjustment of the OBL2 of the OPU 2 is favorably performed for the optical disc (M). Sincethe tilt value other than the reference value 0 stored earlier in thesecond memory circuit 12 is again set as the optimum tilt value in theoptical disc apparatus 1, the optimum tilt value is swiftly set again.

Description will then be made of a state when the track jump of the OPU2 is performed if the optimum tilt value is set to the reference value0. Specifically describing the operation of the optical disc apparatus 1from the start to the end of the track jump process when the optimumtilt value is set to the reference value 0, if the optimum tilt value isset to the reference value 0 (FIG. 21, S391: YES, FIGS. 23, 24, 25, and26), the OPU 2 (FIG. 1) is driven to perform the track jump withoutchanging the tilt value (FIG. 21: S393). Since the optimum tilt value iscontinues to be set to the reference value 0, the track jump continuesto be performed by the OPU 2 on the optical disc M/(M) (FIG. 1) in anormal manner. Since the optimum tilt value of the initial setting wasset to the reference value 0 (FIG. 21, S394: YES, FIGS. 23, 24, 25, and26), the tilt value is not changed after the track jump is completed andthe optimum tilt value is maintained at the reference value 0.

The optical disc apparatus 1 shown in FIG. 1 is configured to be capableof executing at least one or more process among the processes selectedfrom a group consisting of the defocus-value setting process, thedetrack-value setting process, and the tilt-value setting process.Therefore, at least one or more optimum values are set in the opticaldisc apparatus 1 among the optimum defocus value, the optimum detrackvalue, and the optimum tilt value.

Specifically, the optical disc apparatus 1 shown in FIG. 1 is theoptical disc apparatus 1 capable of performing the defocus-valueadjusting method of the optical disc apparatus 1. Therefore, the opticaldisc apparatus 1 capable of setting the optimum defocus value can beprovided. The F-drop is prevented and the stable focusing servo isperformed in the optical disc apparatus 1 including the OPU 2.

The optical disc apparatus 1 shown in FIG. 1 is the optical discapparatus 1 capable of performing the detrack-value adjusting method ofthe optical disc apparatus 1. Therefore, the optical disc apparatus 1capable of setting the optimum detrack value can be provided. The trackskip is prevented and the stable tracking servo is performed in theoptical disc apparatus 1 including the OPU 2.

The optical disc apparatus 1 shown in FIG. 1 is the optical discapparatus 1 capable of performing the tilt-value adjusting method of theoptical disc apparatus 1. Therefore, the optical disc apparatus 1capable of setting the optimum tilt value can be provided. The servofailure is prevented and the stable tilt operation is performed in theoptical disc apparatus 1 including the OPU 2.

When a tilt adjustment circuit of the optical disc apparatus 1 is madeup, even if the optical disc (M) disposed in the optical disc apparatus1 is a wobbling disc MA (FIG. 2), the light axis La of the laser beam Lemitted from the LD 3 of the OPU 2 (FIG. 1) is easily maintainedorthogonal to the signal layer Ms of the optical disc MA.

If the wobbling motion occurs in the optical disc (M), the focusingadjustment of the OBL 4 and the focusing tilt adjustment of the OBL 4are performed at the same time. If the wobbling motion occurs in theoptical disc (M), the position of the OBL 4 is adjusted automatically inthe vertical direction Da. Concurrently, the posture of the OBL 4 isautomatically adjusted such that the light axis La of the laser beamhaving passed through the OBL 4 is tilted to the extent of an angle of−Af to +Af. Therefore, the light axis La of the laser beam is alwaysmaintained orthogonal to the signal layer Ms of the optical disc MA, andthe spot Ls formed by condensing the laser beam with the OBL 4 avoidsthe deviation thereof from the pits Mt in a state of being tracked.Therefore, when reading data from the optical disc MA with the use ofthe OPU 2 (FIG. 1), there is easily prevented the occurrence of thefocus drop and the resultant read error of the data of the optical discMA.

The focus drop occurs due to the wobbling of the optical disc (M), theeccentricity of the optical disc (M), the vibration of the optical disc(M), and the impact on the optical disc (M). When reproducing datarecorded in the optical disc (M) or recording data in the optical disc(M) with the use of the optical disc apparatus 1, it is considered thatthe wobbling of the optical disc (M) and the eccentricity of the opticaldisc (M) steadily occurs in the optical disc apparatus 1. On the otherhand, it is considered that the vibration of the optical disc (M) andthe impact on the optical disc (M) suddenly occurs.

When the tilt adjustment circuit of the optical disc apparatus 1 is madeup, even if the optical disc (M) disposed in the optical disc apparatus1 is an eccentric disc MB (FIGS. 4(A) and (B)), the light axis La of thelaser beam L emitted from the LD 3 of the OPU 2 (FIG. 1) is easilymaintained orthogonal to the signal layer Ms of the optical disc MB.

If the eccentric motion occurs in the optical disc (M) (FIG. 4(A) and(B)), the tracking adjustment of the OBL 4 and the tracking tiltadjustment of the OBL 4 are performed at the same time. If the eccentricmotion occurs in the optical disc (M), the position of the OBL 4 isautomatically adjusted in the disc inward/outward direction Db.Concurrently, the posture of the OBL 4 is automatically adjusted even ifthe light axis La of the laser beam having passed through the OBL 4 istilted to the extent of an angle −At to +At. The light axis La of thelaser beam is always maintained orthogonal to the signal layer Ms of theoptical disc MA, and the spot Ls formed by condensing the laser beamwith the OBL 4 avoids the deviation thereof from the pits Mt in a stateof being tracked. Therefore, when reading data from the optical disc MBwith the use of the OPU 2 (FIG. 1), there is easily prevented theoccurrence of the focus drop causing the read error of the data on theoptical disc MB.

If the optical disc (M) disposed in the optical disc apparatus 1 is thewobbling disc MA (FIG. 2) or if the optical disc (M) disposed in theoptical disc apparatus 1 is the eccentric disc MB (FIGS. 4(A) and (B)),the track jump of the OPU 2 becomes easily performed on the optical discMA or the optical disc MB in a normal manner.

Although the optical disc apparatus 1 shown in FIG. 1 is configured tobe capable of executing the three processes that are the defocus-valuesetting process, the detrack-value setting process, and the tilt-valuesetting process, in accordance with the design/specification, etc. ofthe optical disc apparatus 1, for example, there may be configured theoptical disc apparatus 1 capable of executing the two processes that arethe defocus-value setting process and the detrack-value setting process.In accordance with the design/specification, etc. of the optical discapparatus 1, for example, there may be configured the optical discapparatus 1 capable of executing the two processes that are thedetrack-value setting process and the tilt-value setting process. Inaccordance with the design/specification, etc. of the optical discapparatus 1, for example, there may be configured the optical discapparatus 1 capable of executing the two processes that are thetilt-value setting process and the defocus-value setting process.

In accordance with the design/specification, etc. of the optical discapparatus 1, for example, there may be configured the optical discapparatus 1 capable of executing a plurality of processes among thedefocus-value setting process, the detrack-value setting process, andthe tilt-value setting process. There are individually or concurrentlyexecuted the plurality of processes to be required among thedefocus-value setting process, the detrack-value setting process, andthe tilt-value setting process.

For example, the optical disc apparatus 1 is configured as the oneoptical disc apparatus 1 (FIG. 1) where the adjusting method of theoptical disc apparatus 1 capable of setting the optimum defocus value(FIGS. 6A to 12) is combined or used concurrently with the adjustingmethod of the optical disc apparatus 1 capable of setting the optimumdetrack value (FIGS. 13A to 19) and/or the adjusting method of theoptical disc apparatus 1 capable of setting the optimum tilt value(FIGS. 20A to 26).

For example, with making up the optical disc apparatus 1 as above, therecan be provided the optical disc apparatus 1 capable of setting theoptimum detrack value and/or the optimum tilt value in addition to theoptimum defocus value within a relatively short time.

After the optical disc (M): for which the jitter value ispresumed/determined as not good and the detection/check of each of thejitter values is required; is completely disposed in the optical discapparatus 1, the above setting processes are executed. The settingprocesses are executed, for example, within a total time of more than 0second to substantially 60 seconds, preferably, within a total time ofmore than 0 second to substantially 45 seconds, more preferably, withina total time of more than 0 second to substantially 30 seconds.

Therefore, a situation is avoided where one must wait for a long timedue to the setting processes automatically performed by the optical discapparatus 1 from the time when the optical disc (M): for which thejitter value is presumed/determined as not good and the detection/checkof each of the jitter values is required; is completely disposed in theoptical disc apparatus 1 to the time when the maindata/information/signals of the optical disc (M) are started to be read.The setting processes are ideally executed in a short time closer tosubstantially zero seconds as much as possible. Since the total time ofthe setting processes is, for example, within substantially 60 seconds,preferably, within substantially 45 seconds, more preferably, withinsubstantially 30 seconds, a waiting time for the setting processesautomatically executed by the optical disc apparatus 1 is considered tobe within the permissible range of a user/designer, etc. of the opticaldisc apparatus 1.

After the optical disc (M) with good jitter characteristics iscompletely disposed in the optical disc apparatus 1, when the settingprocesses are executed, the setting processes are executed, for example,within a total time of more than 0 second to substantially 15 seconds,preferably, within a total time of more than 0 second to substantially10 seconds, more preferably, within a total time of more than 0 secondto substantially 5 seconds.

Therefore, a situation is avoided where one must wait for a very longtime due to the setting processes automatically performed by the opticaldisc apparatus 1 from the time when the optical disc (M) with goodcharacteristics is completely disposed in the optical disc apparatus 1to the time when the main data/information/signals of the optical disc(M) are started to be read, and the setting processes are swiftlycompleted in a short time. The setting processes are ideally executedwithin a short time closer to substantially zero seconds as much aspossible. Since the total time of the setting processes is, for example,within substantially 15 seconds, preferably, within substantially 10seconds, more preferably, within substantially 5 seconds after theoptical disc M with good characteristics is completely disposed in theoptical disc apparatus 1, for example, a user/designer, etc. of theoptical disc apparatus 1 will not put under stress due to the waitingtime for the setting processes automatically executed by the opticaldisc apparatus 1.

The optical disc apparatus 1 including the OPU 2 can be used for arecording/reproducing apparatus that records data/information/signals,etc. in the various optical discs M and that reproducesdata/information/signals, etc. in the various optical discs M. Theoptical disc apparatus 1 including the OPU 2 can be used for areproduction-only apparatus that reproduces data/information/signals,etc. in the various optical discs.

The OPU 2 is included in the optical disc apparatus 1 incorporated intocomputers, audio/video devices, game machines, and in-vehicle equipments(all not shown), for example. The optical disc apparatus 1 having theOPU 2 can be included in, for example, computers such as notebook-sizedpersonal computers (PC: personal computer), laptop PCs, desktop PCs, andin-vehicle computers, game machines such as computer game machines, andaudio and/or video devices such as CD players/CD recorders and DVDplayers/DVD recorders (all not shown). The optical disc apparatus 1including the OPU 2 can support a plurality of the media M such asCD-series optical discs, DVD-series optical discs, and “Blu-ray”-seriesoptical discs, for example. The optical disc apparatus 1 having the OPU2 can be included in computers, audio and/or video devices, gamemachines, in-vehicle equipments (all not shown), etc. supporting thevarious optical discs M such as “CD”, “DVD”, “HD-DVD”, and “Blu-rayDisc”.

The above embodiments of the present invention are simply forfacilitating the understanding of the present invention and are not inany way to be construed as limiting the present invention. The presentinvention may variously be changed or altered without departing from itsspirit and encompass equivalents thereof.

1. A disc apparatus comprising: a jitter-value detection unit configuredto detect a jitter value based on a signal to be read from a medium; adefocus-value setting unit configured to set a defocus value forfocusing an objective lens in the medium based on the jitter value; anda defocus-value adjusting unit configured to detect the jitter valueevery time the defocus value is changed stepwise within a predeterminedrange of the defocus value including a reference value of the defocusvalue, to obtain an optimum defocus value to be set for thedefocus-value setting unit within a predetermined time period, based ona maximum jitter value and a minimum jitter value of the detected jittervalues.
 2. The disc apparatus of claim 1, comprising a focusingcontrolling unit configured to move the objective lens in the light axisdirection of the objective lens based on the defocus value.
 3. The discapparatus of claim 1, wherein if a difference value between the maximumjitter value and the minimum jitter value is greater than apredetermined difference value, the defocus-value adjusting unit definesthe defocus value corresponding to the minimum jitter value as theoptimum defocus value to be set in the defocus-value setting unit. 4.The disc apparatus of claim 3, wherein if the difference value betweenthe maximum jitter value and the minimum jitter value is smaller thanthe predetermined difference value, the defocus-value adjusting unitdefines the reference value of the defocus value as the optimum defocusvalue to be set in the defocus-value setting unit.
 5. The disc apparatusof claim 1, wherein if the jitter value corresponding to the referencevalue of the defocus value is greater than a predetermined jitter value,the defocus-value adjusting unit detects the jitter value every time thedefocus value is changed stepwise within the predetermined range of thedefocus value including the reference value of the defocus value.
 6. Thedisc apparatus of claim 5, wherein if the jitter value corresponding tothe reference value of the defocus value is smaller than thepredetermined jitter value, the defocus-value adjusting unit defines thereference value of the defocus value as the optimum defocus value to beset in the defocus-value setting unit.
 7. The disc apparatus of claim 1,wherein if the optimum defocus value is a value other than the referencevalue, when a track jump of an optical pickup device including theobjective lens is performed, the defocus-value adjusting unit definesthe reference value as the defocus value to be set in the defocus-valuesetting unit.
 8. The disc apparatus of claim 7, wherein after the trackjump of the optical pickup device including the objective lens iscompleted, the defocus-value adjusting unit returns the defocus value tobe set in the defocus-value setting unit to a value other than thereference value.
 9. A disc apparatus comprising: a jitter-valuedetection unit configured to detect a jitter value based on a signal tobe read from a medium; a detrack-value setting unit configured to set adetrack value for focusing an objective lens in the medium based on thejitter value; and a detrack-value adjusting unit configured to detectthe jitter value every time the detrack value is changed stepwise withina predetermined range of the detrack value including a reference valueof the detrack value, to obtain an optimum detrack value to be set inthe detrack-value setting unit, based on a maximum jitter value and aminimum jitter value of the detected jitter values.
 10. The discapparatus of claim 9, comprising a tracking controlling unit configuredto move the objective lens in the radial direction of the medium basedon the detrack value.
 11. The disc apparatus of claim 9, wherein if adifference value between the maximum jitter value and the minimum jittervalue is greater than a predetermined difference value, thedetrack-value adjusting unit defines the detrack value corresponding tothe minimum jitter value as the optimum detrack value to be set in thedetrack-value setting unit.
 12. The disc apparatus of claim 11, whereinif the difference value between the maximum jitter value and the minimumjitter value is smaller than the predetermined difference value, thedetrack-value adjusting unit defines the reference value of the detrackvalue as the optimum detrack value to be set in the detrack-valuesetting unit.
 13. The disc apparatus of claim 9, wherein if the jittervalue corresponding to the reference value of the detrack value isgreater than a predetermined jitter value, the detrack-value adjustingunit detects the jitter value every time the detrack value is changedstepwise within the predetermined range of the detrack value includingthe reference value of the detrack value.
 14. The disc apparatus ofclaim 13, wherein if the jitter value corresponding to the referencevalue of the detrack value is smaller than the predetermined jittervalue, the detrack-value adjusting unit defines the reference value ofthe detrack value as the optimum detrack value to be set in thedetrack-value setting unit.
 15. The disc apparatus of claim 9, whereinif the optimum detrack value is a value other than the reference value,when a track jump of an optical pickup device including the objectivelens is performed, the detrack-value adjusting unit defines thereference value as the detrack value to be set in the detrack-valuesetting unit.
 16. The disc apparatus of claim 15, wherein after thetrack jump of the optical pickup device including the objective lens iscompleted, the detrack-value adjusting unit returns the detrack value tobe set in the detrack-value setting unit to a value other than thereference value.
 17. A disc apparatus comprising: a jitter valuedetection unit configured to detect a jitter value based on a signal tobe read from a medium; a tilt-value setting unit configured to set atilt value for focusing an objective lens in the medium based on thejitter value; and a tilt-value adjusting unit configured to detect thejitter value every time the tilt value is changed stepwise within apredetermined range of the tilt value including a reference value of thetilt value, to obtain an optimum tilt value to be set in the tilt-valuesetting unit based on a maximum jitter value and a minimum jitter valueof the detected jitter values.
 18. The disc apparatus of claim 17,comprising a tilt controlling unit configured to correct angulardisplacement of the objective lens relative to a signal layer of themedium based on the tilt value.
 19. The disc apparatus of claim 17,wherein if a difference value between the maximum jitter value and theminimum jitter value is greater than a predetermined difference value,the tilt-value adjusting unit defines the tilt value corresponding tothe minimum jitter value as the optimum tilt value to be set in thetilt-value setting unit.
 20. The disc apparatus of claim 19, wherein ifthe difference value between the maximum jitter value and the minimumjitter value is smaller than the predetermined difference value, thetilt-value adjusting unit defines the reference value of the tilt valueas the optimum tilt value to be set in the tilt-value setting unit. 21.The disc apparatus of claim 17, wherein if the jitter valuecorresponding to the reference value of the tilt value is greater than apredetermined jitter value, the tilt-value adjusting unit detects thejitter value every time the tilt value is changed stepwise within thepredetermined range of the tilt value including the reference value ofthe tilt value.
 22. The disc apparatus of claim 21, wherein if thejitter value corresponding to the reference value of the tilt value issmaller than the predetermined jitter value, the tilt-value adjustingunit defines the reference value of the tilt value as the optimum tiltvalue to be set in the tilt-value setting unit.
 23. The disc apparatusof claim 17, wherein if the optimum tilt value is a value other than thereference value, when a track jump of an optical pickup device includingthe objective lens is performed, the tilt-value adjusting unit definesthe reference value as the tilt value to be set in the tilt-valuesetting unit.
 24. The disc apparatus of claim 23, wherein after thetrack jump of the optical pickup device including the objective lens iscompleted, the tilt-value adjusting unit returns the tilt value to beset in the tilt-value setting unit to a value other than the referencevalue.